fusl/src/network/netlink.c

#include <errno.h>
#include <string.h>
#include <syscall.h>
#include <sys/socket.h>
#include "netlink.h"

static int __netlink_enumerate(int fd,
                               unsigned int seq,
                               int type,
                               int af,
                               int (*cb)(void* ctx, struct nlmsghdr* h),
                               void* ctx) {
  struct nlmsghdr* h;
  union {
    uint8_t buf[8192];
    struct {
      struct nlmsghdr nlh;
      struct rtgenmsg g;
    } req;
    struct nlmsghdr reply;
  } u;
  int r, ret;

  memset(&u.req, 0, sizeof(u.req));
  u.req.nlh.nlmsg_len = sizeof(u.req);
  u.req.nlh.nlmsg_type = type;
  u.req.nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST;
  u.req.nlh.nlmsg_seq = seq;
  u.req.g.rtgen_family = af;
  r = send(fd, &u.req, sizeof(u.req), 0);
  if (r < 0)
    return r;

  while (1) {
    r = recv(fd, u.buf, sizeof(u.buf), MSG_DONTWAIT);
    if (r <= 0)
      return -1;
    for (h = &u.reply; NLMSG_OK(h, (void*)&u.buf[r]); h = NLMSG_NEXT(h)) {
      if (h->nlmsg_type == NLMSG_DONE)
        return 0;
      if (h->nlmsg_type == NLMSG_ERROR)
        return -1;
      ret = cb(ctx, h);
      if (ret)
        return ret;
    }
  }
}

int __rtnetlink_enumerate(int link_af,
                          int addr_af,
                          int (*cb)(void* ctx, struct nlmsghdr* h),
                          void* ctx) {
  int fd, r;

  fd = socket(PF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE);
  if (fd < 0)
    return -1;
  r = __netlink_enumerate(fd, 1, RTM_GETLINK, link_af, cb, ctx);
  if (!r)
    r = __netlink_enumerate(fd, 2, RTM_GETADDR, addr_af, cb, ctx);
  __syscall(SYS_close, fd);
  return r;
}