Added netwatch

diff --git a/netwatch.c b/netwatch.c
new file mode 100755 (executable)
index 0000000..72320ed
--- /dev/null
+++ b/netwatch.c
@@ -0,0 +1,254 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <poll.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include <arpa/inet.h>
+#include <linux/if.h>
+#include <linux/rtnetlink.h>
+
+#include "netwatch.h"
+
+#define NL_BUFSIZE 8192
+
+
+/* yeah, these callbacks really shouldn't be global */
+
+static void *user_data = NULL;
+static NW_IpChangeCallback   on_ip_change   = NULL;
+static NW_LinkChangeCallback on_link_change = NULL;
+
+static void   netwatch_handle_ifaddrmsg (struct nlmsghdr *nl_msg);
+static void   netwatch_handle_ifinfomsg (struct nlmsghdr *nl_msg);
+
+
+int
+netwatch_open (void)
+{
+  int fd;
+  struct sockaddr_nl  local;
+
+  /* Create Socket */
+  if ((fd = socket (PF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE)) < 0)
+    return -1;
+
+  memset (&local, 0, sizeof (local));
+  local.nl_family = AF_NETLINK;
+  local.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR;
+
+  if (bind (fd, (struct sockaddr*) &local, sizeof (local)) < 0)
+    return -1;
+
+  if (fcntl (fd, F_SETFL, O_NONBLOCK))
+    return -1;
+
+  return fd;
+}
+
+int
+netwatch_queue_inforequest (int fd)
+{
+  char buf[NLMSG_LENGTH (sizeof (struct ifaddrmsg))];
+  struct nlmsghdr    *nl_msg;
+
+  bzero (buf, sizeof(buf));
+  nl_msg = (struct nlmsghdr *) buf;
+
+  /* For getting interface addresses */
+  nl_msg->nlmsg_len   = NLMSG_LENGTH (sizeof (struct ifaddrmsg));
+  nl_msg->nlmsg_type  = RTM_GETADDR;
+  nl_msg->nlmsg_flags = NLM_F_ROOT | NLM_F_REQUEST;
+  nl_msg->nlmsg_pid   = getpid ();
+
+  return write (fd, nl_msg, nl_msg->nlmsg_len);
+}
+
+
+int
+netwatch_dispatch (int fd)
+{
+  struct nlmsghdr    *nl_msg;
+  char buf[NL_BUFSIZE];
+  int len, count;
+
+  count = 0;
+  if ((len = recv (fd, buf, NL_BUFSIZE, 0)) < 0)
+    {
+      return (errno == EAGAIN) ? 0 : -1;
+    }
+
+  for (nl_msg = (struct nlmsghdr *) buf;
+       NLMSG_OK (nl_msg, len);
+       nl_msg = NLMSG_NEXT (nl_msg, len))
+    {
+      switch (nl_msg->nlmsg_type)
+        {
+          case RTM_NEWADDR:
+          case RTM_DELADDR:
+            netwatch_handle_ifaddrmsg (nl_msg);
+            break;
+          case RTM_NEWLINK:
+          case RTM_DELLINK:
+            netwatch_handle_ifinfomsg (nl_msg);
+            break;
+          case NLMSG_DONE:
+            break;
+          default:
+            fprintf (stderr, "unhandled message (%d)\n",
+                     nl_msg->nlmsg_type);
+            break;
+        }
+
+      count++;
+    }
+  return count;
+}
+
+
+void
+netwatch_register_callbacks (NW_IpChangeCallback    ip_cb,
+                             NW_LinkChangeCallback  link_cb,
+                             void                  *userdata)
+{
+  user_data = userdata;
+  on_ip_change = ip_cb;
+  on_link_change = link_cb;
+}
+
+
+static void
+netwatch_handle_ifaddrmsg (struct nlmsghdr *nl_msg)
+{
+  struct ifaddrmsg *if_msg;
+  struct rtattr    *attrib;
+  int len;
+
+  char  address[100];
+  char *label = NULL;
+
+  if_msg = (struct ifaddrmsg *) NLMSG_DATA (nl_msg);
+
+  if (if_msg->ifa_family != AF_INET)
+    return;
+
+  address[0] = '\0';
+
+  len = IFA_PAYLOAD (nl_msg);
+  for (attrib = IFA_RTA (if_msg);
+       RTA_OK (attrib, len);
+       attrib = RTA_NEXT (attrib, len))
+    {
+      switch (attrib->rta_type)
+        {
+          case IFA_LOCAL:
+            inet_ntop (AF_INET, RTA_DATA (attrib), address, sizeof (address));
+            break;
+
+          case IFA_LABEL:
+            label = (char *) RTA_DATA (attrib);
+            break;
+
+          default:
+            /* ignore all other attributes */
+            break;
+        }
+    }
+
+  /* if we got both a label and an IP address */
+  if (on_ip_change && label && address[0] &&
+      (nl_msg->nlmsg_type == RTM_NEWADDR || nl_msg->nlmsg_type == RTM_DELADDR))
+    {
+      on_ip_change (if_msg->ifa_index, label, address,
+                    nl_msg->nlmsg_type == RTM_NEWADDR, user_data);
+    }
+
+  return;
+}
+
+
+static void
+netwatch_handle_ifinfomsg (struct nlmsghdr *nl_msg)
+{
+  static unsigned long have_state = 0;
+  static unsigned long linkstate = 0;
+  struct ifinfomsg *ifi;
+
+  ifi = (struct ifinfomsg *) NLMSG_DATA (nl_msg);
+
+  if (on_link_change && ifi->ifi_index < sizeof (unsigned long) * 8)
+    {
+      if (!((1 << ifi->ifi_index) & have_state) ||
+          ((ifi->ifi_flags & IFF_RUNNING) && !((1 << ifi->ifi_index) & linkstate)) ||
+          (!(ifi->ifi_flags & IFF_RUNNING) && ((1 << ifi->ifi_index) & linkstate)))
+        {
+          have_state |= (1 << ifi->ifi_index);
+          if (ifi->ifi_flags & IFF_RUNNING)
+            linkstate |= (1 << ifi->ifi_index);
+          else
+            linkstate &= ~(1 << ifi->ifi_index);
+
+          on_link_change (ifi->ifi_index,
+                          ifi->ifi_flags & IFF_RUNNING ? 1 : 0,
+                          user_data);
+        }
+    }
+}
+
+
+
+#ifdef NETWATCH_MAIN
+void
+print_ip_change (int    link_index,
+                 char  *label,
+                 char  *ipaddr,
+                 int    add,
+                 void  *user_data)
+{
+  fprintf (stdout, "Link No. %d %s address %s (label %s)\n",
+           link_index, add ? "got" : "lost", ipaddr, label);
+}
+
+
+void print_link_change (int   link_index,
+                        int   running,
+                        void *user_data)
+{
+  fprintf (stdout, "Link No. %d is %sconnected\n",
+           link_index, running ? "" : "no longer ");
+}
+
+
+int
+main (int argc, char *argv[])
+{
+  struct pollfd       pollfd;
+  int fd;
+
+  netwatch_register_callbacks (print_ip_change, print_link_change, NULL);
+
+  fd = netwatch_open ();
+  if (fd < 0)
+    {
+      perror ("Error opening netlink socket");
+      exit (1);
+    }
+
+  netwatch_queue_inforequest (fd);
+
+  while (1)
+    {
+      pollfd.fd = fd;
+      pollfd.events = POLLIN;
+      pollfd.revents = 0;
+
+      if (poll (&pollfd, 1, 20000))
+        netwatch_dispatch (fd);
+    }
+
+  close (fd);
+  return 0;
+}
+#endif

diff --git a/netwatch.h b/netwatch.h
new file mode 100755 (executable)
index 0000000..e33c029
--- /dev/null
+++ b/netwatch.h
@@ -0,0 +1,22 @@
+#ifndef __NETWATCH_H__
+#define __NETWATCH_H__
+
+typedef void (* NW_IpChangeCallback)   (int    link_index,
+                                        char  *label,
+                                        char  *ipaddr,
+                                        int    add,
+                                        void  *user_data);
+
+typedef void (* NW_LinkChangeCallback) (int   link_index,
+                                        int   running,
+                                        void *user_data);
+
+int   netwatch_open               (void);
+int   netwatch_queue_inforequest  (int fd);
+int   netwatch_dispatch           (int fd);
+
+void  netwatch_register_callbacks (NW_IpChangeCallback    ip_cb,
+                                   NW_LinkChangeCallback  link_cb,
+                                   void                  *userdata);
+
+#endif /* __NETWATCH_H__ */