Merge #1289

1289: Add Netlink Protocol Families to SockProtocol enum r=asomers a=sinkingpoint

Currently the SockProtocol enum is rather scarce. This commit adds the Netlink protocols
defined in netlink(7) to the SockProtocol enum allowing us to use the Nix socket library for
more in-depth Netlink work. 

Because of the way libc sockets work, this is a bit more annoying than it has any right to be - the Socket Family and the Socket protocol are intertwined in that a given c_int protocol can represent different things depending on the family. This means that as we add values to this enum we're going to get collisions (Indeed, I've left out a few values that collided with the existing TCP/UDP Protocols). I'm not sure how we would want to handle this going forward - maybe different Protocol enums for different Familys, with `Into<SockProtocol>` methods?

I followed the existing pattern in this file when adding these, but perhaps as this enum gets bigger, we should use the libc_enum macro for cleanliness?

Co-authored-by: sinkingpoint <colin@quirl.co.nz>

CHANGELOG.md

@@ -4,6 +4,8 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased] - ReleaseDate
+- Added Netlink protocol families to the `SockProtocol` enum
+(#[1289](https://github.com/nix-rust/nix/pull/1289))
 ### Added
 ### Changed
 ### Fixed

src/sys/socket/mod.rs

@@ -92,6 +92,64 @@ pub enum SockProtocol {
     /// ([ref](https://developer.apple.com/library/content/documentation/Darwin/Conceptual/NKEConceptual/control/control.html))
     #[cfg(any(target_os = "ios", target_os = "macos"))]
     KextControl = libc::SYSPROTO_CONTROL,
+    /// Receives routing and link updates and may be used to modify the routing tables (both IPv4 and IPv6), IP addresses, link
+    // parameters, neighbor setups, queueing disciplines, traffic classes and packet classifiers
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkRoute = libc::NETLINK_ROUTE,
+    /// Reserved for user-mode socket protocols
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkUserSock = libc::NETLINK_USERSOCK,
+    /// Query information about sockets of various protocol families from the kernel
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkSockDiag = libc::NETLINK_SOCK_DIAG,
+    /// SELinux event notifications.
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkSELinux = libc::NETLINK_SELINUX,
+    /// Open-iSCSI
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkISCSI = libc::NETLINK_ISCSI,
+    /// Auditing
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkAudit = libc::NETLINK_AUDIT,
+    /// Access to FIB lookup from user space
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkFIBLookup = libc::NETLINK_FIB_LOOKUP,
+    /// Netfilter subsystem
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkNetFilter = libc::NETLINK_NETFILTER,
+    /// SCSI Transports
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkSCSITransport = libc::NETLINK_SCSITRANSPORT,
+    /// Infiniband RDMA
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkRDMA = libc::NETLINK_RDMA,
+    /// Transport IPv6 packets from netfilter to user space.  Used by ip6_queue kernel module.
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkIPv6Firewall = libc::NETLINK_IP6_FW,
+    /// DECnet routing messages
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkDECNetRoutingMessage = libc::NETLINK_DNRTMSG,
+    /// Kernel messages to user space
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkKObjectUEvent = libc::NETLINK_KOBJECT_UEVENT,
+    /// Netlink interface to request information about ciphers registered with the kernel crypto API as well as allow
+    /// configuration of the kernel crypto API.
+    /// ([ref](https://www.man7.org/linux/man-pages/man7/netlink.7.html))
+    #[cfg(any(target_os = "android", target_os = "linux"))]
+    NetlinkCrypto = libc::NETLINK_CRYPTO,
 }
 
 libc_bitflags!{