From fd38ddb892369547c94d86414b4830bec14cd8c1 Mon Sep 17 00:00:00 2001
From: Jeremy Lakeman <jeremy.lakeman@flinders.edu.au>
Date: Mon, 23 Nov 2015 09:47:45 +1030
Subject: [PATCH] Attempt to recover from transient network errors

---
 overlay_interface.c | 47 ++++++++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 18 deletions(-)

diff --git a/overlay_interface.c b/overlay_interface.c
index a068edc6..483c9689 100644
--- a/overlay_interface.c
+++ b/overlay_interface.c
@@ -59,6 +59,7 @@ struct profile_total sock_any_stats;
 
 static void overlay_interface_poll(struct sched_ent *alarm);
 static int inet_up_count=0;
+static void rescan_soon();
 
 void overlay_interface_close(overlay_interface *interface)
 {
@@ -1058,18 +1059,23 @@ int overlay_broadcast_ensemble(struct network_destination *destination, struct o
 		  bytes, (size_t)len, 0, 
 		  &destination->address.addr, destination->address.addrlen);
 	if (sent == -1){
-	  if (errno!=EAGAIN && errno!=EWOULDBLOCK && errno!=ENOENT && errno!=ENOTDIR)
+	  if (errno!=EAGAIN && errno!=EWOULDBLOCK && errno!=ENOENT && errno!=ENOTDIR){
 	    WHYF_perror("sendto(fd=%d,len=%zu,addr=%s) on interface %s",
 		interface->alarm.poll.fd,
 		(size_t)len,
 		alloca_socket_address(&destination->address),
 		interface->name
 	      );
-	  // close the interface if we had any error while sending broadcast packets,
-	  // unicast packets should not bring the interface down
-	  // TODO mark unicast destination as failed?
-	  if (destination == interface->destination)
-	    overlay_interface_close(interface);
+	    
+	    // if we had any error while sending broadcast packets,
+	    // it could be because the interface is coming down
+	    // or there might be some socket error that we can't fix.
+	    // So bring the interface down, and scan for network changes soon
+	    if (destination == interface->destination){
+	      overlay_interface_close(interface);
+	      rescan_soon();
+	    }
+	  }
 	  ob_free(buffer);
 	  return -1;
 	}
@@ -1279,7 +1285,7 @@ static int netlink_socket()
   return sock;
 }
 
-static int netlink_send_get(int fd)
+static int netlink_send_get()
 {
   struct {
     struct nlmsghdr n;
@@ -1294,6 +1300,7 @@ static int netlink_send_get(int fd)
   struct rtattr *rta = (struct rtattr *)(((char *)&req) + NLMSG_ALIGN(req.n.nlmsg_len));
   rta->rta_len = RTA_LENGTH(4);
   
+  int fd = ALARM_STRUCT(netlink_poll).poll.fd;
   if (send(fd, &req, req.n.nlmsg_len, 0)<0)
     return WHYF_perror("send(%d)", fd);
   
@@ -1315,7 +1322,7 @@ static int netlink_init()
     watch(alarm);
   }
   
-  return netlink_send_get(alarm->poll.fd);
+  return 0;
 }
 
 #else
@@ -1406,6 +1413,18 @@ static void file_interface_init(const struct config_network_interface *ifconfig)
   overlay_interface_init(ifconfig->file, &addr, &netmask, &broadcast, ifconfig);
 }
 
+static void rescan_soon(){
+#ifdef HAVE_LINUX_NETLINK_H
+  // start listening for network changes & request current interface addresses
+  netlink_init();
+  netlink_send_get();
+#else
+  // re-check all interfaces periodically
+  time_ms_t now = gettime_ms();
+  RESCHEDULE(&ALARM_STRUCT(overlay_interface_discover), now, now, now);
+#endif
+}
+
 void overlay_interface_config_change()
 {
   unsigned i;
@@ -1449,16 +1468,8 @@ void overlay_interface_config_change()
     file_interface_init(ifconfig);
   }
   
-  if (real_interface){
-#ifdef HAVE_LINUX_NETLINK_H
-    // start listening for network changes & request current interface addresses
-    netlink_init();
-#else
-    // re-check all interfaces periodically
-    time_ms_t now = gettime_ms();
-    RESCHEDULE(&ALARM_STRUCT(overlay_interface_discover), now, now, now);
-#endif
-  }
+  if (real_interface)
+    rescan_soon();
 }
 
 void logServalPacket(int level, struct __sourceloc __whence, const char *message, const unsigned char *packet, size_t len) {