Module neli::consts

C constants defined as types

High level notes

The items in this module are created by macros, which give them the traits necessary to be serialized into Netlink compatible types. The macros are exported - you can use them too! See impl_var, impl_trait, and impl_var_trait.

Note that most of these constants come from the Linux kernel headers, which can be found in /usr/include/linux on many distros. You can also see man 3 netlink, man 7 netlink, and man 7 rtnetlink for more information.

Design decisions

• Macros are exported so that these conventions are extensible and usable for data types implemented by the user in the case of new netlink families (which is supported by the protocol). In this case, there is no way in which I can support every custom netlink family but my aim is to make this library as flexible as possible so that it is painless to hook your custom netlink data type into the existing library support.
• Enums are used so that:
  • Values can be checked based on a finite number of inputs as opposed to the range of whatever integer data type C defines as the struct member type. This hopefully makes it easier to catch garbage responses and corruption when an invalid netlink message is sent to the kernel.
  • Only the enum or an enum implementing a marker trait in the case of generics can be used in the appropriate places when constructing netlink messages. This takes guess work out of which constants can be used where. Netlink documentation is not always complete and sometimes takes a bit of trial and error actually sending messages to the kernel to figure out if you are using the correct constants. This setup should let you know at compile time if you are doing something you should not be doing.
• UnrecognizedVariant is included in each enum because completeness cannot be guaranteed for every constant for every protocol. This allows you to inspect the integer value returned and if you are sure that it is correct, you can use it. If it is a garbage value, this can also be useful for error reporting.

Enums

AddrFamily	General address families for sockets
Af	Internet address families
Arphrd	Interface types
CtrlAttr	Values for nla_type in Nlattr
CtrlAttrMcastGrp	Values for nla_type in Nlattr
CtrlCmd	Values for cmd in Genlmsghdr
GenlId	Values for nl_type in Nlmsghdr
Ifa	Enum for use with Rtattr.rta_type
IfaF	Interface address flags
Iff	Values for ifi_flags in Ifinfomsg
Ifla	Enum for use with Rtattr.rta_type
NlFamily	Values for nl_family in NlSocket
NlmF	Values for nl_flags in Nlmsghdr
Nlmsg	Values for nl_type in Nlmsghdr
Ntf	Arp neighbor cache entry flags
Nud	Arp neighbor cache entry states
RtScope	rtm_scope The distance between destinations
RtTable	rt_class_t Reserved route table identifiers
Rta	Enum for use with Rtattr.rta_type - Values are routing message attributes
RtmF	rtm_flags Flags for rtnetlink messages
Rtn	rtm_type The results of a lookup from a route table
Rtprot	rtm_protocol The origins of routes that are defined in the kernel
Tca	Enum for use with Rtattr.rta_type - Values specify queuing discipline attributes

Traits

Cmd	Trait marking constants valid for use in Genlmsghdr.cmd
NlAttrType	Marker trait for types usable in Nlattr.nla_type
NlType	Trait marking constants valid for use in Nlmsghdr.nl_type
RtaType	Marker trait for Rtattr.rta_type field

Functions

alignto

Reimplementation of alignto macro in C