--- gvpe/src/vpn.C	2015/07/15 23:04:06	1.68
+++ gvpe/src/vpn.C	2015/09/05 17:40:22	1.69
@@ -61,6 +61,32 @@
 
 /////////////////////////////////////////////////////////////////////////////
 
+// hopefully temporary workaround for rare buffer full conditions
+// if it happens, usually instantly retrying or retrying ~5ms later
+// is good enough with current network technologies/kernels
+
+static ssize_t
+xsendto (int fd, const void *buf, size_t len, int flags,
+         const struct sockaddr *sa, socklen_t salen)
+{
+  ssize_t res;
+
+  for (int retry = 0; retry <= 13; ++retry) // ~100ms
+    {
+      res = sendto (fd, buf, len, flags, sa, salen);
+
+      if (res >= 0 || errno != ENOBUFS)
+        break;
+
+      struct timespec ts = { 0, 1000 * retry };
+      nanosleep (&ts, 0);
+    }
+
+  return res;
+}
+
+/////////////////////////////////////////////////////////////////////////////
+
 static void inline
 set_tos (int fd, int &tos_prev, int tos)
 {
@@ -462,7 +488,7 @@
 vpn::send_ipv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
 {
   set_tos (ipv4_fd, ipv4_tos, tos);
-  sendto (ipv4_fd, &((*pkt)[0]), pkt->len, 0, si.sav4 (), si.salenv4 ());
+  xsendto (ipv4_fd, &((*pkt)[0]), pkt->len, 0, si.sav4 (), si.salenv4 ());
 
   return true;
 }
@@ -503,7 +529,7 @@
   hdr->checksum = ipv4_checksum ((u16 *)hdr, pkt->len);
 
   set_tos (icmpv4_fd, icmpv4_tos, tos);
-  sendto (icmpv4_fd, &((*pkt)[0]), pkt->len, 0, si.sav4 (), si.salenv4 ());
+  xsendto (icmpv4_fd, &((*pkt)[0]), pkt->len, 0, si.sav4 (), si.salenv4 ());
 
   return true;
 }
@@ -513,7 +539,7 @@
 vpn::send_udpv4_packet (vpn_packet *pkt, const sockinfo &si, int tos)
 {
   set_tos (udpv4_fd, udpv4_tos, tos);
-  sendto (udpv4_fd, &((*pkt)[0]), pkt->len, 0, si.sav4 (), si.salenv4 ());
+  xsendto (udpv4_fd, &((*pkt)[0]), pkt->len, 0, si.sav4 (), si.salenv4 ());
 
   return true;
 }