Module consts

High level notes

The contents of this module are generated mostly by macros, which implement the appropriate traits necessary to both be serialized/deserialized and also provide an additional level of type safety when constructing netlink packets. Some of the traits generated in this module allow netlink structures to implement trait bounds assuring that only compatible constant-based enums are allowed to be passed in as parameters. The macros are exported - you can use them too! See impl_trait and impl_flags for more details.

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 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 type parameters 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 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.

Modules

genl

Constants related to generic netlink

netfilter

Constants related to netfilter netlink integration Constants for netfilter related protocols

nl

Constants related to generic netlink top level headers

rtnl

Constants related to rtnetlink

socket

Constants related to netlink socket operations

Constants

MAX_NL_LENGTH

Max supported message length for netlink messages supported by the kernel.

Functions

alignto

Reimplementation of alignto macro in C