aegis-tool 0.4.13

/*
Copyright (c) 2007, 2008 by Juliusz Chroboczek

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <time.h>

#include "babeld.h"
#include "util.h"
#include "net.h"
#include "interface.h"
#include "source.h"
#include "neighbour.h"
#include "route.h"
#include "kernel.h"
#include "xroute.h"
#include "resend.h"
#include "message.h"
#include "configuration.h"
#include "hmac.h"

unsigned char packet_header[4] = {42, 2};

int split_horizon = 1;

unsigned short myseqno = 0;
struct timeval seqno_time = {0, 0};

#define MAX_CHANNEL_HOPS 20

/* Checks whether an AE exists or must be silently ignored */
static int
known_ae(int ae)
{
    return ae <= AE_IPV6_LOCAL || ae == AE_V4VIAV6;
}

/* Parse a network prefix, encoded in the somewhat baroque compressed
   representation used by Babel.  Return the number of bytes parsed. */
static int
network_prefix(int ae, int plen, unsigned int omitted,
               const unsigned char *p, const unsigned char *dp,
               unsigned int len, unsigned char *p_r)
{
    unsigned pb;
    unsigned char prefix[16];
    int ret = -1;

    if(plen >= 0)
        pb = (plen + 7) / 8;
    else if(ae == 1)
        pb = 4;
    else
        pb = 16;

    if(pb > 16)
        return -1;

    memset(prefix, 0, 16);

    switch(ae) {
    case AE_WILDCARD:
        ret = 0;
        break;
    case AE_IPV4:
    case AE_V4VIAV6:
        if(omitted > 4 || pb > 4 || (pb > omitted && len < pb - omitted))
            return -1;
        memcpy(prefix, v4prefix, 12);
        if(omitted) {
            if(dp == NULL || !v4mapped(dp)) return -1;
            memcpy(prefix, dp, 12 + omitted);
        }
        if(pb > omitted) memcpy(prefix + 12 + omitted, p, pb - omitted);
        ret = pb - omitted;
        break;
    case AE_IPV6:
        if(omitted > 16 || (pb > omitted && len < pb - omitted)) return -1;
        if(omitted) {
            if(dp == NULL || v4mapped(dp)) return -1;
            memcpy(prefix, dp, omitted);
        }
        if(pb > omitted) memcpy(prefix + omitted, p, pb - omitted);
        ret = pb - omitted;
        break;
    case AE_IPV6_LOCAL:
        if(pb > 8 && len < pb - 8) return -1;
        prefix[0] = 0xfe;
        prefix[1] = 0x80;
        if(pb > 8) memcpy(prefix + 8, p, pb - 8);
        ret = pb - 8;
        break;
    default:
        return -1;
    }

    normalize_prefix(p_r, prefix,
                     plen < 0 ? 128 : ae_is_v4(ae) ? plen + 96 : plen);
    return ret;
}

static int
parse_update_subtlv(struct interface *ifp, int metric, int ae,
                    const unsigned char *a, int alen,
                    unsigned char *src_prefix, unsigned char *src_plen)
{
    int type, len, i = 0;
    int have_src_prefix = 0;

    while(i < alen) {
        type = a[i];
        if(type == SUBTLV_PAD1) {
            i++;
            continue;
        }

        if(i + 2 > alen)
            goto fail;
        len = a[i + 1];
        if(i + len + 2 > alen)
            goto fail;

        if(type == SUBTLV_PADN) {
            /* Nothing. */
        } else if(type == SUBTLV_SOURCE_PREFIX) {
            int rc;
            if(len < 1)
                goto fail;
            if(a[i + 2] == 0)   /* source prefix cannot be default */
                goto fail;
            if(have_src_prefix != 0) /* source prefix can only appear once */
                goto fail;
            rc = network_prefix(ae, a[i + 2], 0, a + i + 3, NULL,
                                len - 1, src_prefix);
            if(rc < 0)
                goto fail;
            if(ae_is_v4(ae))
                *src_plen = a[i + 2] + 96;
            else
                *src_plen = a[i + 2];
            have_src_prefix = 1;
        } else {
            debugf("Received unknown%s Update sub-TLV %d.\n",
                   (type & 0x80) != 0 ? " mandatory" : "", type);
            if((type & 0x80) != 0)
                return -1;
        }

        i += len + 2;
    }
    return 1;

 fail:
    fprintf(stderr, "Received truncated sub-TLV on Update.\n");
    return -1;
}

static int
parse_hello_subtlv(const unsigned char *a, int alen,
                   unsigned int *timestamp_return, int *have_timestamp_return)
{
    int type, len, i = 0, have_timestamp = 0;
    unsigned int timestamp = 0;

    while(i < alen) {
        type = a[i];
        if(type == SUBTLV_PAD1) {
            i++;
            continue;
        }

        if(i + 2 > alen) {
            fprintf(stderr, "Received truncated sub-TLV on Hello.\n");
            return -1;
        }
        len = a[i + 1];
        if(i + len + 2 > alen) {
            fprintf(stderr, "Received truncated sub-TLV on Hello.\n");
            return -1;
        }

        if(type == SUBTLV_PADN) {
            /* Nothing to do. */
        } else if(type == SUBTLV_TIMESTAMP) {
            if(len >= 4) {
                DO_NTOHL(timestamp, a + i + 2);
                have_timestamp = 1;
            } else {
                fprintf(stderr,
                        "Received incorrect RTT sub-TLV on Hello.\n");
                /* But don't break. */
            }
        } else {
            debugf("Received unknown%s Hello sub-TLV %d.\n",
                   (type & 0x80) != 0 ? " mandatory" : "", type);
            if((type & 0x80) != 0)
                return -1;
        }

        i += len + 2;
    }
    if(have_timestamp && timestamp_return)
        *timestamp_return = timestamp;
    if(have_timestamp_return)
        *have_timestamp_return = have_timestamp;
    return 1;
}

static int
parse_ihu_subtlv(const unsigned char *a, int alen,
                 unsigned int *timestamp1_return,
                 unsigned int *timestamp2_return,
                 int *have_timestamp_return)
{
    int type, len, i = 0;
    int have_timestamp = 0;
    unsigned int timestamp1 = 0, timestamp2 = 0;

    while(i < alen) {
        type = a[i];
        if(type == SUBTLV_PAD1) {
            i++;
            continue;
        }

        if(i + 2 > alen) {
            fprintf(stderr, "Received truncated sub-TLV on IHU.\n");
            return -1;
        }

        len = a[i + 1];
        if(i + len + 2 > alen) {
            fprintf(stderr, "Received truncated sub-TLV on IHU.\n");
            return -1;
        }

        if(type == SUBTLV_PADN) {
            /* Nothing to do. */
        } else if(type == SUBTLV_TIMESTAMP) {
            if(len >= 8) {
                DO_NTOHL(timestamp1, a + i + 2);
                DO_NTOHL(timestamp2, a + i + 6);
                have_timestamp = 1;
            } else {
                fprintf(stderr,
                        "Received incorrect RTT sub-TLV on IHU.\n");
                /* But don't break. */
            }
        } else {
            debugf("Received unknown%s IHU sub-TLV %d.\n",
                   (type & 0x80) != 0 ? " mandatory" : "", type);
            if((type & 0x80) != 0)
                return -1;
        }

        i += len + 2;
    }
    if(have_timestamp && timestamp1_return && timestamp2_return) {
        *timestamp1_return = timestamp1;
        *timestamp2_return = timestamp2;
    }
    if(have_timestamp_return)
        *have_timestamp_return = have_timestamp;
    return 1;
}

static int
parse_request_subtlv(int ae, const unsigned char *a, int alen,
                     unsigned char *src_prefix, unsigned char *src_plen)
{
    int type, len, i = 0;
    int have_src_prefix = 0;

    while(i < alen) {
        type = a[i];
        if(type == SUBTLV_PAD1) {
            i++;
            continue;
        }

        if(i + 2 > alen)
            goto fail;

        len = a[i + 1];
        if(i + 2 + len > alen)
            goto fail;

        if(type == SUBTLV_PADN) {
            /* Nothing to do. */
        } else if(type == SUBTLV_SOURCE_PREFIX) {
            int rc;
            if(len < 1)
                goto fail;
            if(a[i + 2] == 0)
                goto fail;
            if(have_src_prefix != 0)
                goto fail;
            rc = network_prefix(ae, a[i + 2], 0, a + i + 3, NULL,
                                len - 1, src_prefix);
            if(rc < 0)
                goto fail;
            if(ae_is_v4(ae))
                *src_plen = a[i + 2] + 96;
            else
                *src_plen = a[i + 2];
            have_src_prefix = 1;
        } else {
            debugf("Received unknown%s Route Request sub-TLV %d.\n",
                   ((type & 0x80) != 0) ? " mandatory" : "", type);
            if((type & 0x80) != 0)
                return -1;
        }

        i += len + 2;
    }
    return 1;

 fail:
    fprintf(stderr, "Received truncated sub-TLV on Route Request.\n");
    return -1;
}

static int
parse_seqno_request_subtlv(int ae, const unsigned char *a, int alen,
                           unsigned char *src_prefix, unsigned char *src_plen)
{
    int type, len, i = 0;

    while(i < alen) {
        type = a[i];
        if(type == SUBTLV_PAD1) {
            i++;
            continue;
        }

        if(i + 2 > alen)
            goto fail;
        len = a[i + 1];
        if(i + len + 2 > alen)
            goto fail;

        if(type == SUBTLV_PADN) {
            /* Nothing to do. */
        } else if(type == SUBTLV_SOURCE_PREFIX) {
            int rc;
            if(len < 1)
                goto fail;
            *src_plen = a[i + 2];
            rc = network_prefix(ae, *src_plen, 0, a + i + 3, NULL,
                                len - 1, src_prefix);
            if(rc < 0)
                goto fail;
            if(ae_is_v4(ae))
                (*src_plen) += 96;
        } else {
            debugf("Received unknown%s Route Request sub-TLV %d.\n",
                   ((type & 0x80) != 0) ? " mandatory" : "", type);
            if((type & 0x80) != 0)
                return -1;
        }

        i += len + 2;
    }
    return 1;
 fail:
    fprintf(stderr, "Received truncated sub-TLV on Route Request.\n");
    return -1;
}

static int
parse_other_subtlv(const unsigned char *a, int alen)
{
    int type, len, i = 0;

    while(i < alen) {
        type = a[i];
        if(type == SUBTLV_PAD1) {
            i++;
            continue;
        }

        if(i + 2 > alen)
            goto fail;
        len = a[i + 1];
        if(i + 2 + len > alen)
            goto fail;

        if((type & 0x80) != 0) {
            debugf("Received unknown mandatory sub-TLV %d.\n", type);
            return -1;
        }

        i += len + 2;
    }
    return 1;
 fail:
    fprintf(stderr, "Received truncated sub-TLV.\n");
    return -1;
}

static int
network_address(int ae, const unsigned char *a, unsigned int len,
                unsigned char *a_r)
{
    return network_prefix(ae, -1, 0, a, NULL, len, a_r);
}

static struct neighbour *
preparse_packet(const unsigned char *from, struct interface *ifp,
                const unsigned char *body, int bodylen,
                const unsigned char *to)
{
    int rc, i;
    struct neighbour *neigh = NULL;
    int challenge_success = 0, accept_packet = 0;
    const unsigned char *pc = NULL, *index = NULL, *nonce = NULL;
    int index_len, nonce_len = 0;

    i = 0;
    while(i < bodylen) {
        const unsigned char *message = body + 4 + i;
        unsigned char len, type = message[0];
        if(type == MESSAGE_PAD1) {
            i++;
            continue;
        }
        if(i + 2 > bodylen) {
            fprintf(stderr, "Received truncated message.\n");
            break;
        }
        len = message[1];
        if(i + len + 2 > bodylen) {
            fprintf(stderr, "Received truncated message.\n");
            break;
        }
        if(type == MESSAGE_PC) {
            unsigned int pcnat;

            if(index != NULL)
                goto done;

            if(len < 4) {
                fprintf(stderr, "Received truncated PC TLV.\n");
                break;
            }
            if(len > 4 + 32) {
                fprintf(stderr, "Overlong PC TLV.\n");
                break;
            }

            pc = message + 2;
            index = message + 6;
            index_len = len - 4;

            memcpy(&pcnat, pc, 4);
            debugf("Received PC %u from %s.\n",
                   ntohl(pcnat), format_address(from));
        } else if(type == MESSAGE_CHALLENGE_REQUEST) {
            if(to[0] == 0xff)   /* multicast */
                goto done;

            if(len > 192) {
                fprintf(stderr, "Overlong challenge request TLV.\n");
                break;
            }

            nonce = message + 2;
            nonce_len = len;

            debugf("Received challenge request from %s.\n",
                   format_address(from));
        } else if(type == MESSAGE_CHALLENGE_REPLY) {
            if(len > 192) {
                fprintf(stderr, "Overlong challenge reply TLV.\n");
                break;
            }

            debugf("Received challenge reply from %s.\n",
                   format_address(from));

            neigh = neigh != NULL ? neigh : find_neighbour(from, ifp);
            if(neigh == NULL)
                goto done;

            gettime(&now);
            if(timeval_compare(&now, &neigh->challenge_deadline) > 0) {
                debugf("No pending challenge.\n");
                goto done;
            }

            if(len == sizeof(neigh->nonce) &&
               memcmp(neigh->nonce, message + 2, len) == 0) {
                const struct timeval zero = {0, 0};
                challenge_success = 1;
                neigh->challenge_deadline = zero;
                debugf("Challenge succeeded!\n");
            } else {
                debugf("Challenge failed.\n");
            }
        }
    done:
        i += len + 2;
    }

    if(index == NULL) {
        debugf("No PC in packet.\n");
    } else if(challenge_success) {
        neigh->index_len = index_len;
        memcpy(neigh->index, index, index_len);
        memcpy(neigh->pc_m, pc, 4);
        memcpy(neigh->pc_u, pc, 4);
        accept_packet = 1;
    } else {
        neigh = neigh != NULL ? neigh : find_neighbour(from, ifp);
        if(neigh == NULL)
            return NULL;
        if(neigh->index_len == -1 ||
           neigh->index_len != index_len ||
           memcmp(index, neigh->index, index_len) != 0) {
            rc = send_challenge_request(neigh);
            if(rc < -1)
                fputs("Could not send challenge request.\n", stderr);
        } else {
            unsigned char *last_pc;
            if(to[0] == 0xff)
                last_pc = neigh->pc_m;
            else
                last_pc = neigh->pc_u;
            if(memcmp(pc, last_pc, 4) <= 0) {
                debugf("Out of order PC.\n");
                nonce = NULL;
            } else {
                memcpy(last_pc, pc, 4);
                accept_packet = 1;
            }
        }
    }

    if(nonce != NULL) { /* a challenge request was received */
        neigh = neigh != NULL ? neigh : find_neighbour(from, ifp);
        if(neigh == NULL)
            return NULL;
        send_challenge_reply(neigh, nonce, nonce_len);
    }
    debugf("accept_packet: %d, neigh: %p.\n", accept_packet, (void*)neigh);
    return accept_packet ? neigh : NULL;
}

void
parse_packet(const unsigned char *from, struct interface *ifp,
             const unsigned char *packet, int packetlen,
             const unsigned char *to)
{
    int i;
    const unsigned char *message;
    unsigned char type, len;
    int bodylen;
    struct neighbour *neigh = NULL;
    int have_router_id = 0, have_v4_prefix = 0, have_v6_prefix = 0,
        have_v4viav6_prefix = 0,
        have_v4_nh = 0, have_v6_nh = 0;
    unsigned char router_id[8], v4_prefix[16], v6_prefix[16],
        v4viav6_prefix[16], v4_nh[16], v6_nh[16];
    int have_hello_rtt = 0;
    /* Content of the RTT sub-TLV on IHU messages. */
    unsigned int hello_send_us = 0, hello_rtt_receive_time = 0;

    if((ifp->flags & IF_TIMESTAMPS) != 0) {
        /* We want to track exactly when we received this packet. */
        gettime(&now);
    }

    if(!linklocal(from)) {
        fprintf(stderr, "Received packet from non-local address %s.\n",
                format_address(from));
        return;
    }

    if(packet[0] != 42) {
        fprintf(stderr, "Received malformed packet on %s from %s.\n",
                ifp->name, format_address(from));
        return;
    }

    if(packet[1] != 2) {
        fprintf(stderr,
                "Received packet with unknown version %d on %s from %s.\n",
                packet[1], ifp->name, format_address(from));
        return;
    }

    DO_NTOHS(bodylen, packet + 2);

    if(bodylen + 4 > packetlen) {
        fprintf(stderr, "Received truncated packet (%d + 4 > %d).\n",
                bodylen, packetlen);
        bodylen = packetlen - 4;
    }

    if(ifp->key != NULL) {
        int rc = check_hmac(packet, packetlen, bodylen, from, to, ifp);
        if(rc <= 0) {
            if(rc < 0)
                debugf("Received unsigned packet.\n");
            else
                debugf("Received packet with bad signature.\n");
            if(!(ifp->flags & IF_ACCEPT_BAD_SIGNATURES))
                return;
        } else {
            neigh = preparse_packet(from, ifp, packet, bodylen, to);
            if(neigh == NULL) {
                debugf("PC check failed.\n");
                return;
            }
        }
    }

    if(neigh == NULL)
        neigh = find_neighbour(from, ifp);
    if(neigh == NULL) {
        fprintf(stderr, "Couldn't allocate neighbour.\n");
        return;
    }

    i = 0;
    while(i < bodylen) {
        message = packet + 4 + i;
        type = message[0];
        if(type == MESSAGE_PAD1) {
            debugf("Received pad1 from %s on %s.\n",
                   format_address(from), ifp->name);
            i++;
            continue;
        }
        if(i + 2 > bodylen) {
            fprintf(stderr, "Received truncated message.\n");
            break;
        }
        len = message[1];
        if(i + len + 2 > bodylen) {
            fprintf(stderr, "Received truncated message.\n");
            break;
        }

        if(type == MESSAGE_PADN) {
            debugf("Received pad%d from %s on %s.\n",
                   len, format_address(from), ifp->name);
        } else if(type == MESSAGE_ACK_REQ) {
            unsigned short nonce, interval;
            int rc;
            if(len < 6) goto fail;
            DO_NTOHS(nonce, message + 4);
            DO_NTOHS(interval, message + 6);
            debugf("Received ack-req (%04X %d) from %s on %s.\n",
                   nonce, interval, format_address(from), ifp->name);
            rc = parse_other_subtlv(message + 8, len - 6);
            if(rc < 0)
                goto done;
            send_ack(neigh, nonce, interval);
        } else if(type == MESSAGE_ACK) {
            int rc;
            debugf("Received ack from %s on %s.\n",
                   format_address(from), ifp->name);
            rc = parse_other_subtlv(message + 4, len - 2);
            if(rc < 0)
                goto done;
            /* Nothing right now */
        } else if(type == MESSAGE_HELLO) {
            unsigned short seqno, interval;
            int unicast, changed, have_timestamp, rc;
            unsigned int timestamp;
            if(len < 6) goto fail;
            unicast = !!(message[2] & 0x80);
            DO_NTOHS(seqno, message + 4);
            DO_NTOHS(interval, message + 6);
            debugf("Received hello %d (%d) from %s on %s.\n",
                   seqno, interval,
                   format_address(from), ifp->name);
            /* Sub-TLV handling. */
            rc = parse_hello_subtlv(message + 8, len - 6,
                                    &timestamp, &have_timestamp);
            if(rc < 0)
                goto done;
            changed =
                update_neighbour(neigh,
                                 unicast ? &neigh->uhello : &neigh->hello,
                                 unicast, seqno, interval);
            update_neighbour_metric(neigh, changed);
            if(interval > 0)
                /* Multiply by 3/2 to allow hellos to expire. */
                schedule_neighbours_check(interval * 15, 0);
            if(have_timestamp) {
                neigh->hello_send_us = timestamp;
                neigh->hello_rtt_receive_time = now;
                have_hello_rtt = 1;
            }
        } else if(type == MESSAGE_IHU) {
            unsigned short txcost, interval;
            unsigned char address[16];
            int rc;
            if(len < 6) goto fail;
            if(!known_ae(message[2])) {
                debugf("Received IHU with unknown AE %d. Ignoring.\n",
                       message[2]);
                goto done;
            }
            DO_NTOHS(txcost, message + 4);
            DO_NTOHS(interval, message + 6);
            rc = network_address(message[2], message + 8, len - 6, address);
            if(rc < 0) goto fail;
            debugf("Received ihu %d (%d) from %s on %s for %s.\n",
                   txcost, interval,
                   format_address(from), ifp->name,
                   format_address(address));
            if(message[2] == AE_WILDCARD ||
                    interface_ll_address(ifp, address)) {
                int changed;
                rc = parse_ihu_subtlv(message + 8 + rc, len - 6 - rc,
                                      &hello_send_us, &hello_rtt_receive_time,
                                      NULL);
                if(rc < 0)
                    goto done;
                changed = txcost != neigh->txcost;
                neigh->txcost = txcost;
                neigh->ihu_time = now;
                neigh->ihu_interval = interval;
                update_neighbour_metric(neigh, changed);
                if(interval > 0)
                    /* Multiply by 3/2 to allow neighbours to expire. */
                    schedule_neighbours_check(interval * 45, 0);
            }
        } else if(type == MESSAGE_ROUTER_ID) {
            int rc;
            if(len < 10) {
                have_router_id = 0;
                goto fail;
            }
            memcpy(router_id, message + 4, 8);
            have_router_id = 1;
            debugf("Received router-id %s from %s on %s.\n",
                   format_eui64(router_id), format_address(from), ifp->name);
            rc = parse_other_subtlv(message + 12, len - 10);
            if(rc < 0)
                goto done;
        } else if(type == MESSAGE_NH) {
            unsigned char nh[16];
            int rc;
            if(len < 2) {
                have_v4_nh = 0;
                have_v6_nh = 0;
                goto fail;
            }
            rc = network_address(message[2], message + 4, len - 2, nh);
            if(!known_ae(message[2])) {
                debugf("Received NH with unknown AE %d. Ignoring.\n",
                       message[2]);
                goto done;
            }
            if(message[2] == 0) {
                debugf("Received NH with bad AE 0. Error.\n");
                goto fail;
            }
            if(rc < 0) {
                have_v4_nh = 0;
                have_v6_nh = 0;
                goto fail;
            }
            debugf("Received nh %s (%d) from %s on %s.\n",
                   format_address(nh), message[2],
                   format_address(from), ifp->name);
            switch(message[2]) {
            case AE_IPV4:
                memcpy(v4_nh, nh, 16);
                have_v4_nh = 1;
                break;
            case AE_IPV6:
            case AE_IPV6_LOCAL:
                memcpy(v6_nh, nh, 16);
                have_v6_nh = 1;
                break;
            case AE_V4VIAV6:
                goto done;
            default:
                /* We should have guards against this before this point. */
                goto fail;
            }
            rc = parse_other_subtlv(message + 4 + rc, len - 2 - rc);
            if(rc < 0)
                goto done;
        } else if(type == MESSAGE_UPDATE) {
            unsigned char prefix[16], src_prefix[16], *nh;
            unsigned char plen, src_plen;
            unsigned short interval, seqno, metric;
            int rc, parsed_len, is_ss;
            if(len < 10) {
                if(len < 2 || message[3] & 0x80)
                    have_v4_prefix = have_v6_prefix = have_v4viav6_prefix = 0;
                goto fail;
            }
            if(!known_ae(message[2])) {
                debugf("Received update with unknown AE %d. Ignoring.\n",
                       message[2]);
                goto done;
            }
            if(message[2] == AE_V4VIAV6 && !has_v4viav6) {
                /* We can safely ignore the prefix update that might come
                   alongside with this TLV, since we ignore every v4-via-v6
                   TLVs */
                debugf("Ignoring v4-via-v6 route (unsupported).\n");
                goto done;
            }
            DO_NTOHS(interval, message + 6);
            DO_NTOHS(seqno, message + 8);
            DO_NTOHS(metric, message + 10);
            if(message[5] == 0 ||
               (message[2] == AE_IPV4 ? have_v4_prefix :
                message[2] == AE_IPV6 ? have_v6_prefix :
                message[2] == AE_V4VIAV6 ? have_v4viav6_prefix :
                0))
                rc = network_prefix(message[2], message[4], message[5],
                                    message + 12,
                                    (message[2] == AE_IPV4 ? v4_prefix :
                                     message[2] == AE_IPV6 ? v6_prefix :
                                     message[2] == AE_V4VIAV6 ?  v4viav6_prefix :
                                     NULL),
                                    len - 10, prefix);
            else
                rc = -1;
            if(ae_is_v4(message[2])) {
                v4tov6(src_prefix, zeroes);
                src_plen = 96;
            } else {
                memcpy(src_prefix, zeroes, 16);
                src_plen = 0;
            }
            if(rc < 0) {
                if(message[3] & 0x80)
                    have_v4_prefix = have_v6_prefix = have_v4viav6_prefix = 0;
                goto fail;
            }
            parsed_len = 10 + rc;

            plen = message[4] + (ae_is_v4(message[2]) ? 96 : 0);

            if(message[3] & 0x80) {
                switch(message[2]) {
                case AE_IPV4:
                    memcpy(v4_prefix, prefix, 16);
                    have_v4_prefix = 1;
                    break;
                case AE_IPV6:
                    memcpy(v6_prefix, prefix, 16);
                    have_v6_prefix = 1;
                    break;
                case AE_V4VIAV6:
                    memcpy(v4viav6_prefix, prefix, 16);
                    have_v4viav6_prefix = 1;
                    break;
                default:
                    debugf("Received default prefix update with invalid "
                           "AE %d.\n",
                           message[2]);
                    break;
                }
            }
            if(message[3] & 0x40) {
                if(ae_is_v4(message[2])) {
                    memset(router_id, 0, 4);
                    memcpy(router_id + 4, prefix + 12, 4);
                } else {
                    memcpy(router_id, prefix + 8, 8);
                }
                have_router_id = 1;
            }
            if(metric < INFINITY &&
               !have_router_id &&
               message[2] != AE_WILDCARD) {
                fprintf(stderr, "Received prefix with no router id.\n");
                goto fail;
            }
            debugf("Received update%s%s for %s from %s on %s.\n",
                   (message[3] & 0x80) ? "/prefix" : "",
                   (message[3] & 0x40) ? "/id" : "",
                   format_prefix(prefix, plen),
                   format_address(from), ifp->name);
            if(message[2] == AE_IPV4) {
                if(have_v4_nh) {
                    nh = v4_nh;
                } else {
                    if(metric < INFINITY)
                        goto fail;
                    nh = NULL;
                }
            } else if(have_v6_nh) {
                nh = v6_nh;
            } else {
                nh = neigh->address;
            }

            rc = parse_update_subtlv(ifp, metric, message[2],
                                     message + 2 + parsed_len,
                                     len - parsed_len, src_prefix, &src_plen);
            if(rc < 0)
                goto done;

            if(message[2] == AE_WILDCARD) {
                if(metric < 0xFFFF) {
                    fprintf(stderr,
                            "Received wildcard update with finite metric.\n");
                    goto done;
                }
                if(src_plen > 0) {
                    fprintf(stderr,
                            "Received wildcard update with source prefix.\n");
                    goto done;
                }
                retract_neighbour_routes(neigh);
                goto done;
            }

            is_ss = !is_default(src_prefix, src_plen);
            debugf("Received update%s%s for dst %s%s%s from %s on %s.\n",
                   (message[3] & 0x80) ? "/prefix" : "",
                   (message[3] & 0x40) ? "/id" : "",
                   format_prefix(prefix, plen),
                   is_ss ? " src " : "",
                   is_ss ? format_prefix(src_prefix, src_plen) : "",
                   format_address(from), ifp->name);

            update_route(have_router_id ? router_id : NULL,
                         prefix, plen, src_prefix, src_plen, seqno,
                         metric, interval, neigh, nh);
        } else if(type == MESSAGE_REQUEST) {
            unsigned char prefix[16], src_prefix[16], plen, src_plen;
            int rc, is_ss;
            if(len < 2) goto fail;
            if(!known_ae(message[2])) {
                debugf("Received request with unknown AE %d. Ignoring.\n",
                       message[2]);
                goto done;
            }
            rc = network_prefix(message[2], message[3], 0,
                                message + 4, NULL, len - 2, prefix);
            if(rc < 0) goto fail;
            plen = message[3] + (ae_is_v4(message[2]) ? 96 : 0);
            if(ae_is_v4(message[2])) {
                v4tov6(src_prefix, zeroes);
                src_plen = 96;
            } else {
                memcpy(src_prefix, zeroes, 16);
                src_plen = 0;
            }
            rc = parse_request_subtlv(message[2], message + 4 + rc,
                                      len - 2 - rc, src_prefix, &src_plen);
            if(rc < 0)
                goto done;
            is_ss = !is_default(src_prefix, src_plen);
            if(message[2] == AE_WILDCARD) {
                if(is_ss) {
                    /* Wildcard requests don't carry a source prefix. */
                    fprintf(stderr,
                            "Received source-specific wildcard request.\n");
                    goto done;
                }
                debugf("Received request for any from %s on %s.\n",
                       format_address(from), ifp->name);
                /* If a neighbour is requesting a full route dump from us,
                   we might as well send it an IHU. */
                send_ihu(neigh, NULL);
                /* Since nodes send wildcard requests on boot, booting
                   a large number of nodes at the same time may cause an
                   update storm.  Ignore a wildcard request that happens
                   shortly after we sent a full update. */
                if(neigh->ifp->last_update_time <
                   now.tv_sec - MAX(neigh->ifp->hello_interval / 100, 1)) {
                    send_update(neigh->ifp, 0, NULL, 0, NULL, 0);
                }
            } else {
                debugf("Received request for dst %s%s%s from %s on %s.\n",
                       message[2] == AE_WILDCARD ?
                                     "" : format_prefix(prefix, plen),
                       is_ss ? " src " : "",
                       is_ss ? format_prefix(src_prefix, src_plen) : "",
                       format_address(from), ifp->name);
                send_update(neigh->ifp, 0, prefix, plen, src_prefix, src_plen);
            }
        } else if(type == MESSAGE_MH_REQUEST) {
            unsigned char prefix[16], src_prefix[16], plen, src_plen;
            unsigned short seqno;
            int rc, is_ss;
            if(len < 14) goto fail;
            if(!known_ae(message[2])) {
                debugf("Received mh_request with unknown AE %d. Ignoring.\n",
                       message[2]);
                goto done;
            }
            DO_NTOHS(seqno, message + 4);
            rc = network_prefix(message[2], message[3], 0,
                                message + 16, NULL, len - 14, prefix);
            if(rc < 0) goto fail;
            if(ae_is_v4(message[2])) {
                v4tov6(src_prefix, zeroes);
                src_plen = 96;
            } else {
                memcpy(src_prefix, zeroes, 16);
                src_plen = 0;
            }
            rc = parse_seqno_request_subtlv(message[2], message + 16 + rc,
                                            len - 14 - rc, src_prefix,
                                            &src_plen);
            if(rc < 0)
                goto done;
            is_ss = !is_default(src_prefix, src_plen);
            plen = message[3] + (ae_is_v4(message[2]) ? 96 : 0);
            debugf("Received request (%d) for dst %s%s%s from %s on "
                   "%s (%s, %d).\n",
                   message[6],
                   format_prefix(prefix, plen),
                   is_ss ? " src " : "",
                   is_ss ? format_prefix(src_prefix, src_plen) : "",
                   format_address(from), ifp->name,
                   format_eui64(message + 8), seqno);
            handle_request(neigh, prefix, plen, src_prefix, src_plen,
                           message[6], seqno, message + 8);
        } else if(type == MESSAGE_PC ||
                  type == MESSAGE_CHALLENGE_REQUEST ||
                  type == MESSAGE_CHALLENGE_REPLY) {
            /* We're dealing with these in preparse_packet. */
        } else {
            debugf("Received unknown packet type %d from %s on %s.\n",
                   type, format_address(from), ifp->name);
        }
    done:
        i += len + 2;
        continue;

    fail:
        fprintf(stderr, "Couldn't parse packet (%d, %d) from %s on %s.\n",
                message[0], message[1], format_address(from), ifp->name);
        goto done;
    }

    /* We can calculate the RTT to this neighbour. */
    if(have_hello_rtt && hello_send_us && hello_rtt_receive_time) {
        int remote_waiting_us, local_waiting_us;
        unsigned int rtt, smoothed_rtt;
        unsigned int old_rttcost;
        int changed = 0;
        remote_waiting_us = neigh->hello_send_us - hello_rtt_receive_time;
        local_waiting_us = time_us(neigh->hello_rtt_receive_time) -
            hello_send_us;

        /* Sanity checks (validity window of 10 minutes). */
        if(remote_waiting_us < 0 || local_waiting_us < 0 ||
           remote_waiting_us > 600000000 || local_waiting_us > 600000000)
            return;

        rtt = MAX(0, local_waiting_us - remote_waiting_us);
        debugf("RTT to %s on %s sample result: %d us.\n",
               format_address(from), ifp->name, rtt);

        old_rttcost = neighbour_rttcost(neigh);
        if(valid_rtt(neigh)) {
            /* Running exponential average. */
            smoothed_rtt = (ifp->rtt_decay * rtt +
                            (256 - ifp->rtt_decay) * neigh->rtt);
            /* Rounding (up or down) to get closer to the sample. */
            neigh->rtt = (neigh->rtt >= rtt) ? smoothed_rtt / 256 :
                (smoothed_rtt + 255) / 256;
        } else {
            /* We prefer to be conservative with new neighbours
               (higher RTT) */
            assert(rtt <= 0x7FFFFFFF);
            neigh->rtt = 2*rtt;
        }
        changed = (neighbour_rttcost(neigh) == old_rttcost ? 0 : 1);
        update_neighbour_metric(neigh, changed);
        neigh->rtt_time = now;
    }
    return;
}

static int
fill_rtt_message(struct buffered *buf, struct interface *ifp)
{
    if((ifp->flags & IF_TIMESTAMPS) != 0 && (buf->hello >= 0)) {
        if(buf->buf[buf->hello + 8] == SUBTLV_PADN &&
           buf->buf[buf->hello + 9] == 4) {
            unsigned int time;
            /* Change the type of sub-TLV. */
            buf->buf[buf->hello + 8] = SUBTLV_TIMESTAMP;
            gettime(&now);
            time = time_us(now);
            DO_HTONL(buf->buf + buf->hello + 10, time);
            return 1;
        } else {
            fprintf(stderr,
                    "No space left for timestamp sub-TLV "
                    "(this shouldn't happen)\n");
            return -1;
        }
    }
    return 0;
}

void
flushbuf(struct buffered *buf, struct interface *ifp)
{
    int rc;
    int end = buf->len;

    assert(buf->len <= buf->size);

    if(buf->len > 0) {
        int probe;
        if(ifp->key != NULL && ifp->key->type != AUTH_TYPE_NONE)
            send_pc(buf, ifp);
        debugf("  (flushing %d buffered bytes)\n", buf->len);
        DO_HTONS(packet_header + 2, buf->len);
        fill_rtt_message(buf, ifp);
        if(ifp->key != NULL && ifp->key->type != AUTH_TYPE_NONE) {
            end = add_hmac(buf, ifp, packet_header);
            if(end < 0) {
                fprintf(stderr, "Couldn't add HMAC.\n");
                return;
            }
        }
        probe = (ifp->flags & IF_PROBE_MTU) != 0 && ifp->buf.hello >= 0;
        if(probe) {
            /* pad the packet to the MTU */
            while(end < buf->size) {
                if(end + 2 <= buf->size) {
                    /* PadN */
                    int len = buf->size - end - 2;
                    if(len > 255)
                        len = 255;
                    buf->buf[end++] = 1;
                    buf->buf[end++] = len;
                    if(len > 0) {
                        memset(buf->buf + end, 0, len);
                        end += len;
                    }
                } else {
                    /* Pad1 */
                    buf->buf[end++] = 0;
                }
            }
        }

        rc = babel_send(protocol_socket,
                        packet_header, sizeof(packet_header),
                        buf->buf, end,
                        (struct sockaddr*)&buf->sin6,
                        sizeof(buf->sin6), probe);
        if(rc < 0)
            perror("send");
    }
    VALGRIND_MAKE_MEM_UNDEFINED(buf->buf, buf->size);
    buf->len = 0;
    buf->hello = -1;
    buf->have_id = 0;
    buf->have_nh = 0;
    buf->have_prefix = 0;
    buf->timeout.tv_sec = 0;
    buf->timeout.tv_usec = 0;
}

static void
schedule_flush_ms(struct buffered *buf, int msecs)
{
    if(buf->timeout.tv_sec != 0 &&
       timeval_minus_msec(&buf->timeout, &now) < msecs)
        return;
    set_timeout(&buf->timeout, msecs);
}

static void
schedule_flush(struct buffered *buf)
{
    schedule_flush_ms(buf, jitter(buf, 0));
}

static void
schedule_flush_now(struct buffered *buf)
{
    schedule_flush_ms(buf, roughly(10));
}

static void
ensure_space(struct buffered *buf, struct interface *ifp, int space)
{
    if(ifp->key != NULL)
        space += MAX_HMAC_SPACE + 6 + INDEX_LEN;
    if(buf->size - buf->len < space)
        flushbuf(buf, ifp);
}

static void
start_message(struct buffered *buf, struct interface *ifp, int type, int len)
{
    int space = ifp->key == NULL
        ? len + 2
        : len + 2 + MAX_HMAC_SPACE + 6 + INDEX_LEN;
    if(buf->size - buf->len < space)
        flushbuf(buf, ifp);
    buf->buf[buf->len++] = type;
    buf->buf[buf->len++] = len;
}

static void
end_message(struct buffered *buf, int type, int bytes)
{
    assert(buf->len >= bytes + 2 &&
           buf->buf[buf->len - bytes - 2] == type &&
           buf->buf[buf->len - bytes - 1] == bytes);
    schedule_flush(buf);
}

static void
accumulate_byte(struct buffered *buf, unsigned char value)
{
    buf->buf[buf->len++] = value;
}

static void
accumulate_short(struct buffered *buf, unsigned short value)
{
    DO_HTONS(buf->buf + buf->len, value);
    buf->len += 2;
}

static void
accumulate_int(struct buffered *buf, unsigned int value)
{
    DO_HTONL(buf->buf + buf->len, value);
    buf->len += 4;
}

static void
accumulate_bytes(struct buffered *buf,
                 const unsigned char *value, unsigned len)
{
    memcpy(buf->buf + buf->len, value, len);
    buf->len += len;
}

int
send_pc(struct buffered *buf, struct interface *ifp)
{
    int space = MAX_HMAC_SPACE + 6 + INDEX_LEN;
    if(buf->size - buf->len < space) {
        fputs("send_pc: no space left to accumulate pc.\n", stderr);
        return -1;
    }
    if(ifp->pc == 0) {
        int rc;
        rc = read_random_bytes(ifp->index, INDEX_LEN);
        if(rc < INDEX_LEN)
            return -1;
    }
    accumulate_byte(buf, MESSAGE_PC);
    accumulate_byte(buf, 4 + INDEX_LEN);
    accumulate_int(buf, ifp->pc);
    accumulate_bytes(buf, ifp->index, INDEX_LEN);
    ifp->pc++;
    return 0;
}

void
send_ack(struct neighbour *neigh, unsigned short nonce, unsigned short interval)
{
    debugf("Sending ack (%04x) to %s on %s.\n",
           nonce, format_address(neigh->address), neigh->ifp->name);
    start_message(&neigh->buf, neigh->ifp, MESSAGE_ACK, 2);
    accumulate_short(&neigh->buf, nonce);
    end_message(&neigh->buf, MESSAGE_ACK, 2);
    /* Roughly yields a value no larger than 3/2, so this meets the deadline */
    schedule_flush_ms(&neigh->buf, roughly(interval * 6));
}

int
send_challenge_request(struct neighbour *neigh)
{
    int rc;

    gettime(&now);
    if(timeval_compare(&now, &neigh->challenge_request_limitation) <= 0)
        return -1;

    debugf("Sending challenge request to %s on %s.\n",
           format_address(neigh->address), neigh->ifp->name);
    rc = read_random_bytes(neigh->nonce, NONCE_LEN);
    if(rc < NONCE_LEN) {
        perror("read_random_bytes");
        return -2;
    }
    start_message(&neigh->buf, neigh->ifp, MESSAGE_CHALLENGE_REQUEST, NONCE_LEN);
    accumulate_bytes(&neigh->buf, neigh->nonce, NONCE_LEN);
    end_message(&neigh->buf, MESSAGE_CHALLENGE_REQUEST, NONCE_LEN);
    gettime(&now);
    timeval_add_msec(&neigh->challenge_deadline, &now, 30000);
    timeval_add_msec(&neigh->challenge_request_limitation, &now, 300);
    schedule_flush_now(&neigh->buf);
    return 0;
}

int
send_challenge_reply(struct neighbour *neigh, const unsigned char *crypto_nonce,
                     int len)
{
    gettime(&now);
    if(timeval_compare(&now, &neigh->challenge_reply_limitation) <= 0)
        return -1;

    debugf("Sending challenge reply to %s on %s.\n",
           format_address(neigh->address), neigh->ifp->name);
    start_message(&neigh->buf, neigh->ifp, MESSAGE_CHALLENGE_REPLY, len);
    accumulate_bytes(&neigh->buf, crypto_nonce, len);
    end_message(&neigh->buf, MESSAGE_CHALLENGE_REPLY, len);
    gettime(&now);
    timeval_add_msec(&neigh->challenge_reply_limitation, &now, 300);
    schedule_flush_now(&neigh->buf);
    return 0;
}

static void
buffer_hello(struct buffered *buf, struct interface *ifp,
             unsigned short seqno, unsigned interval, int unicast)
{
    int timestamp = !!(ifp->flags & IF_TIMESTAMPS);
    start_message(buf, ifp, MESSAGE_HELLO, timestamp ? 12 : 6);
    buf->hello = buf->len - 2;
    accumulate_short(buf, unicast ? 0x8000 : 0);
    accumulate_short(buf, seqno);
    accumulate_short(buf, interval > 0xFFFF ? 0xFFFF : interval);
    if(timestamp) {
        /* Sub-TLV containing the local time of emission. We use a
           Pad4 sub-TLV, which we'll fill just before sending. */
        accumulate_byte(buf, SUBTLV_PADN);
        accumulate_byte(buf, 4);
        accumulate_int(buf, 0);
    }
    end_message(buf, MESSAGE_HELLO, timestamp ? 12 : 6);
}

void
send_multicast_hello(struct interface *ifp, unsigned interval, int force)
{
    if(!if_up(ifp))
        return;

    if(interval == 0 && (ifp->flags & IF_RFC6126) != 0)
        /* Unscheduled hellos are incompatible with RFC 6126. */
        return;

    /* This avoids sending multiple hellos in a single packet, which breaks
       link quality estimation. */
    if(ifp->buf.hello >= 0) {
        if(force) {
            flushupdates(ifp);
            flushbuf(&ifp->buf, ifp);
        } else {
            return;
        }
    }

    ifp->hello_seqno = seqno_plus(ifp->hello_seqno, 1);
    if(interval > 0)
        set_timeout(&ifp->hello_timeout, ifp->hello_interval);

    debugf("Sending hello %d (%d) to %s.\n",
           ifp->hello_seqno, interval, ifp->name);

    buffer_hello(&ifp->buf, ifp, ifp->hello_seqno, interval, 0);
}

void
send_unicast_hello(struct neighbour *neigh, unsigned interval, int force)
{
    if(!if_up(neigh->ifp))
        return;

    if((neigh->ifp->flags & IF_RFC6126) != 0)
        /* Unicast hellos are incompatible with RFC 6126. */
        return;

    if(neigh->buf.hello >= 0) {
        if(force)
            flushbuf(&neigh->buf, neigh->ifp);
        else
            return;
    }

    neigh->hello_seqno = seqno_plus(neigh->hello_seqno, 1);

    debugf("Sending unicast hello %d (%d) on %s.\n",
           neigh->hello_seqno, interval, neigh->ifp->name);

    buffer_hello(&neigh->buf, neigh->ifp, neigh->hello_seqno, interval, 1);
}

void
send_hello(struct interface *ifp)
{
    send_multicast_hello(ifp, (ifp->hello_interval + 9) / 10, 1);
    /* Send full IHU every 3 hellos, and marginal IHU each time */
    if(ifp->hello_seqno % 3 == 0)
        send_ihu(NULL, ifp);
    else
        send_marginal_ihu(ifp);
}

static void
really_buffer_update(struct buffered *buf, struct interface *ifp,
                     const unsigned char *id,
                     const unsigned char *prefix, unsigned char plen,
                     const unsigned char *src_prefix, unsigned char src_plen,
                     unsigned short seqno, unsigned short metric)
{
    int add_metric, v4, real_plen, real_src_plen;
    int ae, omit, spb, len;
    const unsigned char *real_prefix, *real_src_prefix;
    unsigned short flags = 0;
    int is_ss = !is_default(src_prefix, src_plen);

    if(!if_up(ifp))
        return;

    if(is_ss && (ifp->flags & IF_RFC6126) != 0)
        return;

    add_metric = output_filter(id, prefix, plen, src_prefix,
                               src_plen, ifp->ifindex);
    if(add_metric >= INFINITY)
        return;

    metric = MIN(metric + add_metric, INFINITY);

    /* Worst case */
    ensure_space(buf, ifp, 20 + 12 + 28 + 18);

    v4 = plen >= 96 && v4mapped(prefix);

    if(v4) {
        if(!ifp->ipv4) {
            if((ifp->flags & IF_V4VIAV6) == 0)
                return;
            ae = AE_V4VIAV6;
        } else {
            ae = AE_IPV4;
            if(!buf->have_nh ||
               memcmp(buf->nh, ifp->ipv4, 4) != 0) {
                start_message(buf, ifp, MESSAGE_NH, 6);
                accumulate_byte(buf, AE_IPV4);
                accumulate_byte(buf, 0);
                accumulate_bytes(buf, ifp->ipv4, 4);
                end_message(buf, MESSAGE_NH, 6);
                memcpy(&buf->nh, ifp->ipv4, 4);
                buf->have_nh = 1;
            }
        }
        omit = 0;
        real_prefix = prefix + 12;
        real_plen = plen - 96;
        real_src_prefix = src_prefix + 12;
        real_src_plen = src_plen - 96;
    } else {
        ae = AE_IPV6;
        omit = 0;
        if(buf->have_prefix) {
            while(omit < plen / 8 &&
                  buf->prefix[omit] == prefix[omit])
                omit++;
        }
        if(!buf->have_prefix || plen >= 48)
            flags |= 0x80;
        real_prefix = prefix;
        real_plen = plen;
        real_src_prefix = src_prefix;
        real_src_plen = src_plen;
    }

    if(!buf->have_id || memcmp(id, buf->id, 8) != 0) {
        if(real_plen == 128 && memcmp(real_prefix + 8, id, 8) == 0) {
            flags |= 0x40;
        } else {
            start_message(buf, ifp, MESSAGE_ROUTER_ID, 10);
            accumulate_short(buf, 0);
            accumulate_bytes(buf, id, 8);
            end_message(buf, MESSAGE_ROUTER_ID, 10);
        }
        memcpy(buf->id, id, 8);
        buf->have_id = 1;
    }

    len = 10 + (real_plen + 7) / 8 - omit;
    spb = (real_src_plen + 7) / 8;
    if(is_ss)
        len += 3 + spb;

    start_message(buf, ifp, MESSAGE_UPDATE, len);
    accumulate_byte(buf, ae);
    accumulate_byte(buf, flags);
    accumulate_byte(buf, real_plen);
    accumulate_byte(buf, omit);
    accumulate_short(buf, (ifp->update_interval + 5) / 10);
    accumulate_short(buf, seqno);
    accumulate_short(buf, metric);
    accumulate_bytes(buf, real_prefix + omit, (real_plen + 7) / 8 - omit);
    if(is_ss) {
        accumulate_byte(buf, SUBTLV_SOURCE_PREFIX);
        accumulate_byte(buf, 1 + spb);
        accumulate_byte(buf, real_src_plen);
        accumulate_bytes(buf, real_src_prefix, spb);
    }
    end_message(buf, MESSAGE_UPDATE, len);
    if(flags & 0x80) {
        memcpy(buf->prefix, prefix, 16);
        buf->have_prefix = 1;
    }
}

static void
really_send_update(struct interface *ifp, const unsigned char *id,
                   const unsigned char *prefix, unsigned char plen,
                   const unsigned char *src_prefix, unsigned char src_plen,
                   unsigned short seqno, unsigned short metric)
{
    if(!if_up(ifp))
        return;

    if((ifp->flags & IF_UNICAST) != 0) {
        struct neighbour *neigh;
        FOR_ALL_NEIGHBOURS(neigh) {
            if(neigh->ifp == ifp) {
                really_buffer_update(&neigh->buf, ifp, id,
                                     prefix, plen, src_prefix, src_plen,
                                     seqno, metric);
            }
        }
    } else {
        really_buffer_update(&ifp->buf, ifp, id,
                             prefix, plen, src_prefix, src_plen,
                             seqno, metric);
    }
}

static int
compare_buffered_updates(const void *av, const void *bv)
{
    const struct buffered_update *a = av, *b = bv;
    int rc, v4a, v4b, ma, mb;

    rc = memcmp(a->id, b->id, 8);
    if(rc != 0)
        return rc;

    v4a = (a->plen >= 96 && v4mapped(a->prefix));
    v4b = (b->plen >= 96 && v4mapped(b->prefix));

    if(v4a > v4b)
        return 1;
    else if(v4a < v4b)
        return -1;

    ma = (!v4a && a->plen == 128 && memcmp(a->prefix + 8, a->id, 8) == 0);
    mb = (!v4b && b->plen == 128 && memcmp(b->prefix + 8, b->id, 8) == 0);

    if(ma > mb)
        return -1;
    else if(mb > ma)
        return 1;

    if(a->plen < b->plen)
        return 1;
    else if(a->plen > b->plen)
        return -1;

    rc = memcmp(a->prefix, b->prefix, 16);
    if(rc != 0)
        return rc;

    if(a->src_plen < b->src_plen)
        return -1;
    else if(a->src_plen > b->src_plen)
        return 1;

    return memcmp(a->src_prefix, b->src_prefix, 16);
}

void
flushupdates(struct interface *ifp)
{
    struct xroute *xroute;
    struct babel_route *route;
    const unsigned char *last_prefix = NULL;
    const unsigned char *last_src_prefix = NULL;
    unsigned char last_plen = 0xFF;
    unsigned char last_src_plen = 0xFF;
    int i;

    if(ifp == NULL) {
        struct interface *ifp_aux;
        FOR_ALL_INTERFACES(ifp_aux)
            flushupdates(ifp_aux);
        return;
    }

    if(ifp->num_buffered_updates > 0) {
        struct buffered_update *b = ifp->buffered_updates;
        int n = ifp->num_buffered_updates;

        ifp->buffered_updates = NULL;
        ifp->update_bufsize = 0;
        ifp->num_buffered_updates = 0;

        if(!if_up(ifp))
            goto done;

        debugf("  (flushing %d buffered updates on %s (%d))\n",
               n, ifp->name, ifp->ifindex);

        /* In order to send fewer update messages, we want to send updates
           with the same router-id together, with IPv6 going out before IPv4. */

        for(i = 0; i < n; i++) {
            route = find_installed_route(b[i].prefix, b[i].plen,
                                         b[i].src_prefix, b[i].src_plen);
            if(route)
                memcpy(b[i].id, route->src->id, 8);
            else
                memcpy(b[i].id, myid, 8);
        }

        qsort(b, n, sizeof(struct buffered_update), compare_buffered_updates);

        for(i = 0; i < n; i++) {
            /* The same update may be scheduled multiple times before it is
               sent out.  Since our buffer is now sorted, it is enough to
               compare with the previous update. */

            if(last_prefix &&
               b[i].plen == last_plen &&
               b[i].src_plen == last_src_plen &&
               memcmp(b[i].prefix, last_prefix, 16) == 0 &&
               memcmp(b[i].src_prefix, last_src_prefix, 16) == 0)
                continue;

            xroute = find_xroute(b[i].prefix, b[i].plen,
                                 b[i].src_prefix, b[i].src_plen);
            route = find_installed_route(b[i].prefix, b[i].plen,
                                         b[i].src_prefix, b[i].src_plen);

            if(xroute && (!route || xroute->metric <= kernel_metric)) {
                really_send_update(ifp, myid,
                                   xroute->prefix, xroute->plen,
                                   xroute->src_prefix, xroute->src_plen,
                                   myseqno, xroute->metric);
                last_prefix = xroute->prefix;
                last_plen = xroute->plen;
                last_src_prefix = xroute->src_prefix;
                last_src_plen = xroute->src_plen;
            } else if(route) {
                unsigned short metric;
                unsigned short seqno;

                seqno = route->seqno;
                metric = route_metric(route);

                if(metric < INFINITY)
                    satisfy_request(route->src->prefix, route->src->plen,
                                    route->src->src_prefix,
                                    route->src->src_plen,
                                    seqno, route->src->id, ifp);

                if((ifp->flags & IF_SPLIT_HORIZON) &&
                   route->neigh->ifp == ifp)
                    continue;

                really_send_update(ifp, route->src->id,
                                   route->src->prefix, route->src->plen,
                                   route->src->src_prefix,
                                   route->src->src_plen,
                                   seqno, metric);
                update_source(route->src, seqno, metric);
                last_prefix = route->src->prefix;
                last_plen = route->src->plen;
                last_src_prefix = route->src->src_prefix;
                last_src_plen = route->src->src_plen;
            } else {
            /* There's no route for this prefix.  This can happen shortly
               after an xroute has been retracted, so send a retraction. */
                really_send_update(ifp, myid,
                                   b[i].prefix, b[i].plen,
                                   b[i].src_prefix, b[i].src_plen,
                                   myseqno, INFINITY);
            }
        }

        if((ifp->flags & IF_UNICAST) != 0) {
            struct neighbour *neigh;
            FOR_ALL_NEIGHBOURS(neigh) {
                if(neigh->ifp == ifp) {
                    schedule_flush_now(&neigh->buf);
                }
            }
        } else {
            schedule_flush_now(&ifp->buf);
        }
    done:
        free(b);
    }
    ifp->update_flush_timeout.tv_sec = 0;
    ifp->update_flush_timeout.tv_usec = 0;
}

static void
schedule_update_flush(struct interface *ifp, int urgent)
{
    unsigned msecs;
    msecs = update_jitter(ifp, urgent);
    if(ifp->update_flush_timeout.tv_sec != 0 &&
       timeval_minus_msec(&ifp->update_flush_timeout, &now) < msecs)
        return;
    set_timeout(&ifp->update_flush_timeout, msecs);
}

static void
buffer_update(struct interface *ifp,
              const unsigned char *prefix, unsigned char plen,
              const unsigned char *src_prefix, unsigned char src_plen)
{
    if(ifp->num_buffered_updates > 0 &&
       ifp->num_buffered_updates >= ifp->update_bufsize)
        flushupdates(ifp);

    if(ifp->update_bufsize == 0) {
        int n;
        assert(ifp->buffered_updates == NULL);
        /* Allocate enough space to hold a full update.  Since the
           number of installed routes will grow over time, make sure we
           have enough space to send a full-ish frame. */
        n = installed_routes_estimate() + xroutes_estimate() + 4;
        n = MAX(n, ifp->buf.size / 16);
    again:
        ifp->buffered_updates = malloc(n * sizeof(struct buffered_update));
        if(ifp->buffered_updates == NULL) {
            perror("malloc(buffered_updates)");
            if(n > 4) {
                /* Try again with a tiny buffer. */
                n = 4;
                goto again;
            }
            return;
        }
        ifp->update_bufsize = n;
        ifp->num_buffered_updates = 0;
    }

    memcpy(ifp->buffered_updates[ifp->num_buffered_updates].prefix,
           prefix, 16);
    ifp->buffered_updates[ifp->num_buffered_updates].plen = plen;
    memcpy(ifp->buffered_updates[ifp->num_buffered_updates].src_prefix,
           src_prefix, 16);
    ifp->buffered_updates[ifp->num_buffered_updates].src_plen = src_plen;
    ifp->num_buffered_updates++;
}

/* Full wildcard update with prefix == src_prefix == NULL,
   Standard wildcard update with prefix == NULL && src_prefix != NULL,
   Specific wildcard update with prefix != NULL && src_prefix == NULL. */
void
send_update(struct interface *ifp, int urgent,
            const unsigned char *prefix, unsigned char plen,
            const unsigned char *src_prefix, unsigned char src_plen)
{
    if(ifp == NULL) {
        struct interface *ifp_aux;
        struct babel_route *route;
        FOR_ALL_INTERFACES(ifp_aux)
            send_update(ifp_aux, urgent, prefix, plen, src_prefix, src_plen);
        if(prefix) {
            /* Since flushupdates only deals with non-wildcard interfaces, we
               need to do this now. */
            route = find_installed_route(prefix, plen, src_prefix, src_plen);
            if(route && route_metric(route) < INFINITY)
                satisfy_request(prefix, plen, src_prefix, src_plen,
                                route->src->seqno, route->src->id, NULL);
        }
        return;
    }

    if(!if_up(ifp))
        return;

    if(prefix && src_prefix) {
        debugf("Sending update to %s for %s from %s.\n",
               ifp->name, format_prefix(prefix, plen),
               format_prefix(src_prefix, src_plen));
        buffer_update(ifp, prefix, plen, src_prefix, src_plen);
    } else if(prefix || src_prefix) {
        struct route_stream *routes;
        send_self_update(ifp);
        debugf("Sending update to %s for any.\n", ifp->name);
        routes = route_stream(1);
        if(routes) {
            while(1) {
                int is_ss;
                struct babel_route *route = route_stream_next(routes);
                if(route == NULL)
                    break;
                is_ss = !is_default(route->src->src_prefix,
                                    route->src->src_plen);
                if((src_prefix && is_ss) || (prefix && !is_ss))
                    continue;
                buffer_update(ifp, route->src->prefix, route->src->plen,
                              route->src->src_prefix, route->src->src_plen);
            }
            route_stream_done(routes);
        } else {
            fprintf(stderr, "Couldn't allocate route stream.\n");
        }
        set_timeout(&ifp->update_timeout, ifp->update_interval);
        ifp->last_update_time = now.tv_sec;
    } else {
        send_update(ifp, urgent, NULL, 0, zeroes, 0);
        send_update(ifp, urgent, zeroes, 0, NULL, 0);
    }
    schedule_update_flush(ifp, urgent);
}

void
send_update_resend(struct interface *ifp,
                   const unsigned char *prefix, unsigned char plen,
                   const unsigned char *src_prefix, unsigned char src_plen)
{
    assert(prefix != NULL);

    send_update(ifp, 1, prefix, plen, src_prefix, src_plen);
    record_resend(RESEND_UPDATE, prefix, plen, src_prefix, src_plen,
                  0, NULL, NULL, resend_delay);
}

void
buffer_wildcard_retraction(struct buffered *buf, struct interface *ifp)
{
    start_message(buf, ifp, MESSAGE_UPDATE, 10);
    accumulate_byte(buf, AE_WILDCARD);
    accumulate_byte(buf, 0);
    accumulate_byte(buf, 0);
    accumulate_byte(buf, 0);
    accumulate_short(buf, 0xFFFF);
    accumulate_short(buf, myseqno);
    accumulate_short(buf, 0xFFFF);
    end_message(buf, MESSAGE_UPDATE, 10);

    buf->have_id = 0;
}


void
send_wildcard_retraction(struct interface *ifp)
{
    if(ifp == NULL) {
        struct interface *ifp_aux;
        FOR_ALL_INTERFACES(ifp_aux)
            send_wildcard_retraction(ifp_aux);
        return;
    }

    if(!if_up(ifp))
        return;

    if((ifp->flags & IF_UNICAST) != 0) {
        struct neighbour *neigh;
        FOR_ALL_NEIGHBOURS(neigh) {
            if(neigh->ifp == ifp) {
                buffer_wildcard_retraction(&neigh->buf, neigh->ifp);
            }
        }
    } else {
        buffer_wildcard_retraction(&ifp->buf, ifp);
    }
}

static void
update_myseqno()
{
    myseqno = seqno_plus(myseqno, 1);
    seqno_time = now;
}

void
send_self_update(struct interface *ifp)
{
    struct xroute_stream *xroutes;
    if(ifp == NULL) {
        struct interface *ifp_aux;
        FOR_ALL_INTERFACES(ifp_aux) {
            if(!if_up(ifp_aux))
                continue;
            send_self_update(ifp_aux);
        }
        return;
    }

    debugf("Sending self update to %s.\n", ifp->name);
    xroutes = xroute_stream();
    if(xroutes) {
        while(1) {
            struct xroute *xroute = xroute_stream_next(xroutes);
            if(xroute == NULL) break;
            send_update(ifp, 0, xroute->prefix, xroute->plen,
                        xroute->src_prefix, xroute->src_plen);
        }
        xroute_stream_done(xroutes);
    } else {
        fprintf(stderr, "Couldn't allocate xroute stream.\n");
    }
}

void
buffer_ihu(struct buffered *buf, struct interface *ifp, unsigned short rxcost,
           unsigned short interval, const unsigned char *address,
           int rtt_data, unsigned int t1, unsigned int t2)
{
    int msglen, ll;

    ll = linklocal(address);
    msglen = (ll ? 14 : 22) + (rtt_data ? 10 : 0);

    start_message(buf, ifp, MESSAGE_IHU, msglen);
    accumulate_byte(buf, ll ? AE_IPV6_LOCAL : AE_IPV6);
    accumulate_byte(buf, 0);
    accumulate_short(buf, rxcost);
    accumulate_short(buf, interval);
    if(ll)
        accumulate_bytes(buf, address + 8, 8);
    else
        accumulate_bytes(buf, address, 16);
    if(rtt_data) {
        accumulate_byte(buf, SUBTLV_TIMESTAMP);
        accumulate_byte(buf, 8);
        accumulate_int(buf, t1);
        accumulate_int(buf, t2);
    }
    end_message(buf, MESSAGE_IHU, msglen);
}


void
send_ihu(struct neighbour *neigh, struct interface *ifp)
{
    int rxcost, interval;
    int send_rtt_data;
    int unicast;

    if(neigh == NULL && ifp == NULL) {
        struct interface *ifp_aux;
        FOR_ALL_INTERFACES(ifp_aux) {
            if(if_up(ifp_aux))
                send_ihu(NULL, ifp_aux);
        }
        return;
    }

    if(neigh == NULL) {
        struct neighbour *ngh;
        FOR_ALL_NEIGHBOURS(ngh) {
            if(ngh->ifp == ifp)
                send_ihu(ngh, ifp);
        }
        return;
    }

    if(ifp && neigh->ifp != ifp)
        return;

    ifp = neigh->ifp;
    if(!if_up(ifp))
        return;

    rxcost = neighbour_rxcost(neigh);
    interval = (ifp->hello_interval * 3 + 9) / 10;

    debugf("Sending ihu %d on %s to %s.\n",
           rxcost,
           neigh->ifp->name,
           format_address(neigh->address));

    /* If we already have unicast data buffered for this peer, piggyback
       the IHU.  Only do that if RFC 6126 compatibility is disabled, since
       doing that might require sending an unscheduled unicast Hello. */
    unicast = !!(ifp->flags & IF_UNICAST) ||
        (neigh->buf.len > 0 && !(ifp->flags & IF_RFC6126));


    if(!!(ifp->flags & IF_TIMESTAMPS) != 0 && neigh->hello_send_us &&
       /* Checks whether the RTT data is not too old to be sent. */
       timeval_minus_msec(&now, &neigh->hello_rtt_receive_time) < 1000000) {
        send_rtt_data = 1;
    } else {
        neigh->hello_send_us = 0;
        send_rtt_data = 0;
    }

    if(send_rtt_data) {
        /* Ensure that there is a Hello in the same packet. */
        ensure_space(unicast ? &neigh->buf : &ifp->buf, ifp, 14 + 16);
        if(unicast)
            send_unicast_hello(neigh, 0, 0);
        else
            send_multicast_hello(ifp, 0, 0);
    }

    buffer_ihu(unicast ? &neigh->buf : &ifp->buf,
               ifp, rxcost, interval, neigh->address,
               send_rtt_data, neigh->hello_send_us,
               time_us(neigh->hello_rtt_receive_time));

}

/* Send IHUs to all marginal neighbours */
void
send_marginal_ihu(struct interface *ifp)
{
    struct neighbour *neigh;
    FOR_ALL_NEIGHBOURS(neigh) {
        if(ifp && neigh->ifp != ifp)
            continue;
        if(neigh->txcost >= 384 || (neigh->hello.reach & 0xF000) != 0xF000)
            send_ihu(neigh, ifp);
    }
}

/* Standard wildcard request with prefix == NULL && src_prefix == zeroes,
   Specific wildcard request with prefix == zeroes && src_prefix == NULL. */
static void
send_request(struct buffered *buf, struct interface *ifp,
             const unsigned char *prefix, unsigned char plen,
             const unsigned char *src_prefix, unsigned char src_plen)
{
    int v4, pb, spb, len;
    int is_ss = !is_default(src_prefix, src_plen);

    if(is_ss && (ifp->flags & IF_RFC6126) != 0)
        return;

    if(!prefix) {
        assert(!src_prefix);
        debugf("sending request for any.\n");
        start_message(buf, ifp, MESSAGE_REQUEST, 2);
        accumulate_byte(buf, AE_WILDCARD);
        accumulate_byte(buf, 0);
        end_message(buf, MESSAGE_REQUEST, 2);
        return;
    }

    debugf("sending request for %s from %s.\n",
           format_prefix(prefix, plen),
           format_prefix(src_prefix, src_plen));

    v4 = plen >= 96 && v4mapped(prefix);
    pb = v4 ? ((plen - 96) + 7) / 8 : (plen + 7) / 8;
    spb = v4 ? ((src_plen - 96) + 7) / 8 : (src_plen + 7) / 8;
    len = 2 + pb + (is_ss ? 3 + spb : 0);

    start_message(buf, ifp, MESSAGE_REQUEST, len);
    accumulate_byte(buf, v4 ? AE_IPV4 : AE_IPV6);
    accumulate_byte(buf, v4 ? plen - 96 : plen);
    if(v4)
        accumulate_bytes(buf, prefix + 12, pb);
    else
        accumulate_bytes(buf, prefix, pb);
    if(is_ss) {
        accumulate_byte(buf, SUBTLV_SOURCE_PREFIX);
        accumulate_byte(buf, 1 + spb);
        accumulate_byte(buf, v4 ? src_plen - 96 : src_plen);
        if(v4)
            accumulate_bytes(buf, src_prefix + 12, spb);
        else
            accumulate_bytes(buf, src_prefix, spb);
    }
    end_message(buf, MESSAGE_REQUEST, len);
}

void
send_multicast_request(struct interface *ifp,
                       const unsigned char *prefix, unsigned char plen,
                       const unsigned char *src_prefix, unsigned char src_plen)
{
    if(ifp == NULL) {
        struct interface *ifp_auxn;
        FOR_ALL_INTERFACES(ifp_auxn) {
            if(!if_up(ifp_auxn))
                continue;
            send_multicast_request(ifp_auxn, prefix, plen, src_prefix, src_plen);
        }
        return;
    }

    if(!if_up(ifp))
        return;

    /* make sure any buffered updates go out before this request. */
    flushupdates(ifp);

    if((ifp->flags & IF_UNICAST) != 0) {
        struct neighbour *neigh;
        FOR_ALL_NEIGHBOURS(neigh) {
            if(neigh->ifp == ifp) {
                send_request(&neigh->buf, ifp, prefix, plen,
                             src_prefix, src_plen);
            }
        }
    } else {
        send_request(&ifp->buf, ifp, prefix, plen, src_prefix, src_plen);
    }
}

void
send_unicast_request(struct neighbour *neigh,
                     const unsigned char *prefix, unsigned char plen,
                     const unsigned char *src_prefix, unsigned char src_plen)
{
    if(!if_up(neigh->ifp))
        return;

    flushupdates(neigh->ifp);

    send_request(&neigh->buf, neigh->ifp, prefix, plen, src_prefix, src_plen);
}

static void
send_multihop_request(struct buffered *buf, struct interface *ifp,
                      const unsigned char *prefix, unsigned char plen,
                      const unsigned char *src_prefix, unsigned char src_plen,
                      unsigned short seqno, const unsigned char *id,
                      unsigned short hop_count)
{
    int v4, pb, spb, len;
    int is_ss = !is_default(src_prefix, src_plen);

    if(is_ss && (ifp->flags & IF_RFC6126) != 0)
        return;

    debugf("Sending request (%d) for %s.\n",
           hop_count, format_prefix(prefix, plen));

    v4 = plen >= 96 && v4mapped(prefix);
    pb = v4 ? ((plen - 96) + 7) / 8 : (plen + 7) / 8;
    spb = v4 ? ((src_plen - 96) + 7) / 8 : (src_plen + 7) / 8;
    len = 6 + 8 + pb + (is_ss ? 3 + spb : 0);

    start_message(buf, ifp, MESSAGE_MH_REQUEST, len);
    accumulate_byte(buf, v4 ? AE_IPV4 : AE_IPV6);
    accumulate_byte(buf, v4 ? plen - 96 : plen);
    accumulate_short(buf, seqno);
    accumulate_byte(buf, hop_count);
    accumulate_byte(buf, v4 ? src_plen - 96 : src_plen);
    accumulate_bytes(buf, id, 8);
    if(prefix) {
        if(v4)
            accumulate_bytes(buf, prefix + 12, pb);
        else
            accumulate_bytes(buf, prefix, pb);
    }
    if(is_ss) {
        accumulate_byte(buf, SUBTLV_SOURCE_PREFIX);
        accumulate_byte(buf, 1 + spb);
        accumulate_byte(buf, v4 ? src_plen - 96 : src_plen);
        if(v4)
            accumulate_bytes(buf, src_prefix + 12, spb);
        else
            accumulate_bytes(buf, src_prefix, spb);
    }
    end_message(buf, MESSAGE_MH_REQUEST, len);
}

void
send_multicast_multihop_request(struct interface *ifp,
                      const unsigned char *prefix, unsigned char plen,
                      const unsigned char *src_prefix, unsigned char src_plen,
                      unsigned short seqno, const unsigned char *id,
                      unsigned short hop_count)
{
    if(ifp == NULL) {
        struct interface *ifp_aux;
        FOR_ALL_INTERFACES(ifp_aux) {
            if(!if_up(ifp_aux))
                continue;
            send_multicast_multihop_request(ifp_aux,
                                            prefix, plen, src_prefix, src_plen,
                                            seqno, id, hop_count);
        }
        return;
    }

    flushupdates(ifp);

    if(!if_up(ifp))
        return;

    if((ifp->flags & IF_UNICAST) != 0) {
            struct neighbour *neigh;
            FOR_ALL_NEIGHBOURS(neigh) {
                if(neigh->ifp == ifp) {
                    send_multihop_request(&neigh->buf, neigh->ifp,
                                          prefix, plen,
                                          src_prefix, src_plen,
                                          seqno, id, hop_count);
                }
            }
    } else {
        send_multihop_request(&ifp->buf, ifp,
                              prefix, plen,
                              src_prefix, src_plen,
                              seqno, id, hop_count);
    }

}

void
send_unicast_multihop_request(struct neighbour *neigh,
                              const unsigned char *prefix, unsigned char plen,
                              const unsigned char *src_prefix,
                              unsigned char src_plen,
                              unsigned short seqno, const unsigned char *id,
                              unsigned short hop_count)
{
    flushupdates(neigh->ifp);
    send_multihop_request(&neigh->buf, neigh->ifp,
                          prefix, plen, src_prefix, src_plen,
                          seqno, id, hop_count);
}

/* Send a request to a well-chosen neighbour and resend.  If there is no
   good neighbour, send over multicast but only once. */
void
send_request_resend(const unsigned char *prefix, unsigned char plen,
                    const unsigned char *src_prefix, unsigned char src_plen,
                    unsigned short seqno, unsigned char *id)
{
    struct babel_route *route;

    route = find_best_route(prefix, plen, src_prefix, src_plen, 0, NULL);

    if(route) {
        struct neighbour *neigh = route->neigh;
        send_unicast_multihop_request(neigh, prefix, plen, src_prefix, src_plen,
                                      seqno, id, 127);
        record_resend(RESEND_REQUEST, prefix, plen, src_prefix, src_plen, seqno,
                      id, neigh->ifp, resend_delay);
    } else {
        struct interface *ifp;
        FOR_ALL_INTERFACES(ifp) {
            if(!if_up(ifp)) continue;
            send_multihop_request(&ifp->buf, ifp,
                                  prefix, plen, src_prefix, src_plen,
                                  seqno, id, 127);
        }
    }
}

void
handle_request(struct neighbour *neigh, const unsigned char *prefix,
               unsigned char plen,
               const unsigned char *src_prefix, unsigned char src_plen,
               unsigned char hop_count,
               unsigned short seqno, const unsigned char *id)
{
    struct xroute *xroute;
    struct babel_route *route;
    struct neighbour *successor = NULL;

    xroute = find_xroute(prefix, plen, src_prefix, src_plen);
    route = find_installed_route(prefix, plen, src_prefix, src_plen);

    if(xroute && (!route || xroute->metric <= kernel_metric)) {
        if(hop_count > 0 && memcmp(id, myid, 8) == 0) {
            if(seqno_compare(seqno, myseqno) > 0) {
                if(seqno_minus(seqno, myseqno) > 100) {
                    /* Hopelessly out-of-date request */
                    return;
                }
                update_myseqno();
            }
        }
        send_update(neigh->ifp, 1, prefix, plen, src_prefix, src_plen);
        return;
    }

    if(route &&
       (memcmp(id, route->src->id, 8) != 0 ||
        seqno_compare(seqno, route->seqno) <= 0)) {
        send_update(neigh->ifp, 1, prefix, plen, src_prefix, src_plen);
        return;
    }

    if(hop_count <= 1)
        return;

    if(route && memcmp(id, route->src->id, 8) == 0 &&
       seqno_minus(seqno, route->seqno) > 100) {
        /* Hopelessly out-of-date */
        return;
    }

    if(request_redundant(neigh->ifp, prefix, plen, src_prefix, src_plen,
                         seqno, id))
        return;

    /* Let's try to forward this request. */
    if(route && route_metric(route) < INFINITY)
        successor = route->neigh;

    if(!successor || successor == neigh) {
        /* We were about to forward a request to its requestor.  Try to
           find a different neighbour to forward the request to. */
        struct babel_route *other_route;

        other_route = find_best_route(prefix, plen, src_prefix, src_plen,
                                      0, neigh);
        if(other_route && route_metric(other_route) < INFINITY)
            successor = other_route->neigh;
    }

    if(!successor || successor == neigh)
        /* Give up */
        return;

    send_unicast_multihop_request(successor, prefix, plen, src_prefix, src_plen,
                                  seqno, id, hop_count - 1);
    record_resend(RESEND_REQUEST, prefix, plen, src_prefix, src_plen, seqno, id,
                  neigh->ifp, 0);
}