arcbox_vm_proto/
boot.rs

1//! Boot protocol types shared between the host-side sandbox orchestrator
2//! and the guest-side `vm-agent`.
3//!
4//! These types define the contract passed through kernel boot parameters.
5//! Both sides import from this module so the encoding is defined once.
6
7use std::fmt;
8use std::net::Ipv4Addr;
9use std::str::FromStr;
10
11/// Parsed representation of the Linux kernel `ip=` boot parameter.
12///
13/// Format: `ip=<client>::<gateway>:<netmask>::eth0:off`
14///
15/// Constructed by the sandbox manager
16/// (`arcbox_computer_runtime::ComputerManager`) when building boot args, and
17/// parsed by `vm-agent` to derive the DNS nameserver from the gateway.
18///
19/// [`fmt::Display`] and [`FromStr`] round-trip through the same format so the
20/// encoding is defined exactly once.
21#[derive(Debug, Clone, PartialEq, Eq)]
22pub struct KernelIpParam {
23    /// Guest IP address (the `<client>` field).
24    pub client: Ipv4Addr,
25    /// Gateway IP (also serves as the guest DNS nameserver).
26    pub gateway: Ipv4Addr,
27    /// Subnet mask derived from the network prefix length.
28    pub netmask: Ipv4Addr,
29}
30
31impl fmt::Display for KernelIpParam {
32    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
33        write!(
34            f,
35            "ip={}::{}:{}::eth0:off",
36            self.client, self.gateway, self.netmask,
37        )
38    }
39}
40
41impl FromStr for KernelIpParam {
42    type Err = String;
43
44    /// Parse a kernel `ip=` token (e.g. `ip=172.20.0.2::172.20.0.1:255.255.0.0::eth0:off`).
45    fn from_str(s: &str) -> Result<Self, Self::Err> {
46        let value = s.strip_prefix("ip=").ok_or("missing ip= prefix")?;
47        let mut fields = value.split(':');
48
49        let client = fields
50            .next()
51            .filter(|s| !s.is_empty())
52            .ok_or("missing client field")?
53            .parse::<Ipv4Addr>()
54            .map_err(|e| format!("invalid client IP: {e}"))?;
55
56        // Skip <server> (always empty in our usage).
57        fields.next();
58
59        let gateway = fields
60            .next()
61            .filter(|s| !s.is_empty())
62            .ok_or("missing gateway field")?
63            .parse::<Ipv4Addr>()
64            .map_err(|e| format!("invalid gateway IP: {e}"))?;
65
66        let netmask = fields
67            .next()
68            .filter(|s| !s.is_empty())
69            .ok_or("missing netmask field")?
70            .parse::<Ipv4Addr>()
71            .map_err(|e| format!("invalid netmask: {e}"))?;
72
73        Ok(Self {
74            client,
75            gateway,
76            netmask,
77        })
78    }
79}
80
81/// Network reconfiguration command sent to `vm-agent` over the exec vsock
82/// channel (`MSG_NET_RECONFIG`) after a fresh-network snapshot restore.
83///
84/// A restored VM still carries the network the kernel configured from the
85/// origin's `ip=` boot parameter; when the restore allocated a new TAP/IP
86/// (`network_override`), the host sends this command so the guest
87/// re-addresses `eth0`, replaces the default route, and repoints DNS at the
88/// new gateway. Serialized as JSON, mirroring `StartCommand`.
89#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
90pub struct NetReconfigCommand {
91    /// New guest IP address for `eth0`.
92    pub ip: Ipv4Addr,
93    /// Subnet mask (e.g. 255.255.0.0).
94    pub netmask: Ipv4Addr,
95    /// Gateway IP (also serves as the guest DNS nameserver).
96    pub gateway: Ipv4Addr,
97}
98
99#[cfg(test)]
100mod tests {
101    use super::*;
102
103    #[test]
104    fn roundtrip() {
105        let param = KernelIpParam {
106            client: Ipv4Addr::new(172, 20, 0, 2),
107            gateway: Ipv4Addr::new(172, 20, 0, 1),
108            netmask: Ipv4Addr::new(255, 255, 0, 0),
109        };
110        let s = param.to_string();
111        assert_eq!(s, "ip=172.20.0.2::172.20.0.1:255.255.0.0::eth0:off");
112        assert_eq!(s.parse::<KernelIpParam>().unwrap(), param);
113    }
114
115    #[test]
116    fn rejects_invalid() {
117        assert!("no-prefix".parse::<KernelIpParam>().is_err());
118        assert!("ip=".parse::<KernelIpParam>().is_err());
119        assert!(
120            "ip=bogus::1.2.3.4:255.0.0.0::eth0:off"
121                .parse::<KernelIpParam>()
122                .is_err()
123        );
124    }
125}
arcbox_vm_proto/boot.rs

arcbox_vm_proto/
boot.rs
