1 files changed, 77 insertions, 0 deletions
diff --git a/src/libbcnm/bcnm_if_link_event.c b/src/libbcnm/bcnm_if_link_event.c
new file mode 100644
index 0000000..fd7157a
--- /dev/null
+++ b/src/libbcnm/bcnm_if_link_event.c
@@ -0,0 +1,77 @@
+/* ISC license. */
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <string.h>
+#include <errno.h>
+#include <net/if.h>
+#include <sys/socket.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+
+#include <bcnm/if.h>
+
+static inline ssize_t fd_recvmsg_nb (int fd, struct msghdr *hdr)
+{
+  int e = errno ;
+  ssize_t r ;
+  do r = recvmsg(fd, hdr, MSG_DONTWAIT) ;
+  while (r == -1 && errno == EINTR) ;
+  if (r == -1 && errno == EWOULDBLOCK) return (errno = e, 0) ;
+  if (!r) return (errno = EPIPE, -1) ;
+  return r ;
+}
+
+static int answer (bcnm_if_link_state_t *tab, size_t n, char const *ifname, unsigned int state)
+{
+  size_t i = 0 ;
+  for (; i < n ; i++) if (!strcmp(ifname, tab[i].ifname)) break ;
+  if (i >= n) return 0 ;
+  tab[i].state = state ;
+  tab[i].changed = 1 ;
+  return 1 ;
+}
+
+ssize_t bcnm_if_link_event (int fd, bcnm_if_link_state_t *tab, size_t n)
+{
+  ssize_t e = 0 ;
+  struct sockaddr_nl nl ;
+  struct nlmsghdr buf[8192 / sizeof(struct nlmsghdr)] ;
+  struct iovec v = { .iov_base = buf, .iov_len = sizeof(struct nlmsghdr) * (8192 / sizeof(struct nlmsghdr)) } ;
+  struct msghdr msg =
+  {
+    .msg_name = &nl,
+    .msg_namelen = sizeof(struct sockaddr_nl),
+    .msg_iov = &v,
+    .msg_iovlen = 1,
+    .msg_control = 0,
+    .msg_controllen = 0,
+    .msg_flags = 0
+  } ;
+  ssize_t r = fd_recvmsg_nb(fd, &msg) ;
+  if (r <= 0) return r ;
+  if (msg.msg_flags & MSG_TRUNC) return (errno = ENOBUFS, -1) ;
+  if (nl.nl_pid) return (errno = EPROTO, -1) ;
+  for (struct nlmsghdr *hdr = buf ; NLMSG_OK(hdr, r) ; hdr = NLMSG_NEXT(hdr, r))
+  {
+    struct ifinfomsg *ifi = NLMSG_DATA(hdr) ;
+    char ifname[IF_NAMESIZE] ;
+    switch (hdr->nlmsg_type)
+    {
+      case NLMSG_DONE : goto out ;
+      case NLMSG_ERROR : return (errno = EPROTO, -1) ;
+      case RTM_DELLINK :
+        if_indextoname(ifi->ifi_index, ifname) ;
+        e += answer(tab, n, ifname, 0) ;
+        break ;
+      case RTM_NEWLINK :
+        if_indextoname(ifi->ifi_index, ifname) ;
+        e += answer(tab, n, ifname, 1 | !!(ifi->ifi_flags & IFF_UP) << 1 | !!(ifi->ifi_flags & IFF_RUNNING) << 2) ;
+        break ;
+    }
+  }
+ out:
+  return e ;
+}