diff --git a/ospfd/ChangeLog b/ospfd/ChangeLog
index af5ace4..feba89a 100644
--- a/ospfd/ChangeLog
+++ b/ospfd/ChangeLog
@@ -1,3 +1,16 @@
+2007-08-21 Denis Ovsienko
+
+	* ospfd.h: Extend struct ospf with maxsndbuflen field and
+	  define its default value.
+	* ospfd.c: (ospf_new) init maxsndbuflen
+	* ospf_interface.c: (ospf_if_up) Call ospf_adjust_sndbuflen()
+	  for each regular interface being brought up.
+	* ospf_network.[ch]: (ospf_adjust_sndbuflen) New function
+	  makes sure ospf socket sending buffer is large enough
+	  to cover the biggest interface MTU we have seen ever.
+	* ospf_packet.c: (ospf_write) Use maxsndbuflen to decide on
+	  the biggest amount of data we are going to send at once.
+
 2007-08-07 Paul Jakma <paul.jakma@sun.com>
 
 	* ospf_spf.c: (ospf_spf_next) Finish off the explanatory
diff --git a/ospfd/ospf_interface.c b/ospfd/ospf_interface.c
index bf53668..862735b 100644
--- a/ospfd/ospf_interface.c
+++ b/ospfd/ospf_interface.c
@@ -781,6 +781,11 @@
     OSPF_ISM_EVENT_SCHEDULE (oi, ISM_LoopInd);
   else
     {
+      struct ospf *ospf = ospf_lookup ();
+      if (ospf != NULL)
+        ospf_adjust_sndbuflen (ospf, oi->ifp->mtu);
+      else
+        zlog_warn ("%s: ospf_lookup() returned NULL");
       ospf_if_stream_set (oi);
       OSPF_ISM_EVENT_SCHEDULE (oi, ISM_InterfaceUp);
     }
diff --git a/ospfd/ospf_network.c b/ospfd/ospf_network.c
index e8c9837..11155db 100644
--- a/ospfd/ospf_network.c
+++ b/ospfd/ospf_network.c
@@ -41,6 +41,7 @@
 #include "ospfd/ospf_lsdb.h"
 #include "ospfd/ospf_neighbor.h"
 #include "ospfd/ospf_packet.h"
+#include "ospfd/ospf_dump.h"
 
 
 
@@ -233,3 +234,37 @@
  
   return ospf_sock;
 }
+
+void
+ospf_adjust_sndbuflen (struct ospf * ospf, int buflen)
+{
+  int ret, newbuflen;
+  /* Check if any work has to be done at all. */
+  if (ospf->maxsndbuflen >= buflen)
+    return;
+  if (IS_DEBUG_OSPF (zebra, ZEBRA_INTERFACE))
+    zlog_debug ("%s: adjusting OSPF send buffer size to %d",
+      __func__, buflen);
+  if (ospfd_privs.change (ZPRIVS_RAISE))
+    zlog_err ("%s: could not raise privs, %s", __func__,
+      safe_strerror (errno));
+  /* Now we try to set SO_SNDBUF to what our caller has requested
+   * (OSPF_SNDBUFLEN_DEFAULT initially, which seems to be a sane
+   * default; or the MTU of a newly added interface). However,
+   * if the OS has truncated the actual buffer size to somewhat
+   * less or bigger size, try to detect it and update our records
+   * appropriately.
+   */
+  ret = setsockopt_so_sendbuf (ospf->fd, buflen);
+  newbuflen = getsockopt_so_sendbuf (ospf->fd);
+  if (ret < 0 || newbuflen != buflen)
+    zlog_warn ("%s: tried to set SO_SNDBUF to %d, but got %d",
+      __func__, buflen, newbuflen);
+  if (newbuflen >= 0)
+    ospf->maxsndbuflen = newbuflen;
+  else
+    zlog_warn ("%s: failed to get SO_SNDBUF", __func__);
+  if (ospfd_privs.change (ZPRIVS_LOWER))
+    zlog_err ("%s: could not lower privs, %s", __func__,
+      safe_strerror (errno));
+}
diff --git a/ospfd/ospf_network.h b/ospfd/ospf_network.h
index 1b43df1..f690991 100644
--- a/ospfd/ospf_network.h
+++ b/ospfd/ospf_network.h
@@ -34,5 +34,6 @@
 				     unsigned int);
 extern int ospf_if_ipmulticast (struct ospf *, struct prefix *, unsigned int);
 extern int ospf_sock_init (void);
+extern void ospf_adjust_sndbuflen (struct ospf *, int);
 
 #endif /* _ZEBRA_OSPF_NETWORK_H */
diff --git a/ospfd/ospf_packet.c b/ospfd/ospf_packet.c
index 4735f99..a778a50 100644
--- a/ospfd/ospf_packet.c
+++ b/ospfd/ospf_packet.c
@@ -602,8 +602,12 @@
     ipid = (time(NULL) & 0xffff);
 #endif /* WANT_OSPF_WRITE_FRAGMENT */
 
-  /* convenience - max OSPF data per packet */
-  maxdatasize = oi->ifp->mtu - sizeof (struct ip);
+  /* convenience - max OSPF data per packet,
+   * and reliability - not more data, than our
+   * socket can accept
+   */
+  maxdatasize = MIN (oi->ifp->mtu, ospf->maxsndbuflen) -
+    sizeof (struct ip);
   
   /* Get one packet from queue. */
   op = ospf_fifo_head (oi->obuf);
diff --git a/ospfd/ospfd.c b/ospfd/ospfd.c
index 80b97fa..8133050 100644
--- a/ospfd/ospfd.c
+++ b/ospfd/ospfd.c
@@ -212,6 +212,8 @@
 	       "a socket");
       exit(1);
     }
+  new->maxsndbuflen = 0;
+  ospf_adjust_sndbuflen (new, OSPF_SNDBUFLEN_DEFAULT);
   if ((new->ibuf = stream_new(OSPF_MAX_PACKET_SIZE+1)) == NULL)
     {
       zlog_err("ospf_new: fatal error: stream_new(%u) failed allocating ibuf",
diff --git a/ospfd/ospfd.h b/ospfd/ospfd.h
index ec9d9d6..b0a14ce 100644
--- a/ospfd/ospfd.h
+++ b/ospfd/ospfd.h
@@ -129,6 +129,9 @@
 #define OSPF_LS_REFRESH_SHIFT       (60 * 15)
 #define OSPF_LS_REFRESH_JITTER      60
 
+/* Initial send buffer size for ospfd raw sending socket. */
+#define OSPF_SNDBUFLEN_DEFAULT           1024
+
 /* OSPF master for system wide configuration and variables. */
 struct ospf_master
 {
@@ -266,6 +269,7 @@
   struct thread *t_write;
   struct thread *t_read;
   int fd;
+  int maxsndbuflen;
   struct stream *ibuf;
   struct list *oi_write_q;