Netlink Route support

Netlink Route (NETLINK_ROUTE) allow notifying msg when the network changes. And then apps can obtain these changes by monitoring to netlink socket messages.

NuttX supports Netlink Route groups

• RTMGRP_IPV4_ROUTE | RTMGRP_IPV6_ROUTE - Notify when IPV4|IPV6 routing table changes.

• RTMGRP_NEIGH - Notify when ARP (IPV4) or neighbors (IPV6) table changes.

• RTNLGRP_IPV6_PREFIX - Notify when IPV6 prefix changes.

Messages content

1. RTMGRP_IPV4_ROUTE | RTMGRP_IPV6_ROUTE

RTM_NEWROUTE, RTM_DELROUTE, RTM_GETROUTE: Create, remove or receive information about a network route. These messages contain an rtmsg structure with 3 optional sequence of rtattr structures following.

struct getroute_recvfrom_ipv4addr_s
{
  struct rtattr attr;
  in_addr_t     addr;
};

struct getroute_recvfrom_ipv4response_s
{
  struct nlmsghdr hdr;
  struct rtmsg    rte;
  struct getroute_recvfrom_ipv4addr_s dst;
  struct getroute_recvfrom_ipv4addr_s genmask;
  struct getroute_recvfrom_ipv4addr_s gateway;
};

struct getroute_recvfrom_ipv6addr_s
{
  struct rtattr  attr;
  net_ipv6addr_t addr;
};

struct getroute_recvfrom_ipv6response_s
{
  struct nlmsghdr hdr;
  struct rtmsg    rte;
  struct getroute_recvfrom_ipv6addr_s dst;
  struct getroute_recvfrom_ipv6addr_s genmask;
  struct getroute_recvfrom_ipv6addr_s gateway;
};

2. RTMGRP_NEIGH

RTM_NEWNEIGH, RTM_DELNEIGH, RTM_GETNEIGH: Add, remove or receive information about a neighbor table entry (e.g., an ARP entry). The message contains an ndmsg structure and optional sequence of rtattr structures following. And the date will be struct arpreq in include/netinet/arp.h``or ``struct neighbor_entry_s in include/net/neighbor.h

struct getneigh_recvfrom_response_s
{
  struct nlmsghdr hdr;
  struct ndmsg    msg;
  struct rtattr   attr;
  uint8_t         data[1];
};

3. RTNLGRP_IPV6_PREFIX

RTM_NEWPREFIX: Receive information about IPV6 prefix. The message contains an prefixmsg structure and two optional sequence of rtattr structures following. And the addr and prefix_cacheinfo are parsed from the RA message.

struct getprefix_recvfrom_addr_s
{
  struct rtattr  attr;
  net_ipv6addr_t addr;
};

struct getprefix_recvfrom_cache_s
{
  struct rtattr           attr;
  struct prefix_cacheinfo pci;
};

struct getprefix_recvfrom_response_s
{
  struct nlmsghdr  hdr;
  struct prefixmsg pmsg;
  struct getprefix_recvfrom_addr_s  prefix;
  struct getprefix_recvfrom_cache_s pci;
};

Usage

struct sockaddr_nl addr;
struct nlmsghdr *hdr;
uint8_t buffer[BUFSIZE];
int sd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);

addr.nl_family  = AF_NETLINK;
addr.nl_groups  = RTMGRP_IPV4_ROUTE | RTMGRP_IPV6_ROUTE |
                  RTMGRP_NEIGH | RTMGRP_IPV6_PREFIX;

bind(sd, (FAR struct sockaddr *)&addr, sizeof(addr)); /* Bind to device */
while (1)
  {
    recv(sd, buf, BUFSIZE, 0);
    for (hdr = buf; NLMSG_OK(hdr, ret); hdr = NLMSG_NEXT(hdr, ret))
      {
        if (hdr->nlmsg_type == RTM_...)
          {
            /* Func parsed netlink msg*/
            ...
          }
      }
  }

close(sd); /* Close the socket */