ha: Make receive buffer size for the HA socket configurable

If there are lots of SAs to be synced, the default might be too low
and messages and SAs get dropped.  The new default is already 8 MiB,
which should work fine for lots of SAs.  The code mirrors the one in
the kernel-netlink plugin (but with a guard around SO_RCVBUFFORCE, even
though this plugin is mostly used on Linux as well).

src/libcharon/plugins/ha/ha_socket.c

@@ -28,6 +28,13 @@
 #include <threading/thread.h>
 #include <processing/jobs/callback_job.h>
 
+/**
+ * Default receive buffer size
+ */
+#ifndef HA_SOCKET_RCVBUF_DEFAULT
+#define HA_SOCKET_RCVBUF_DEFAULT (8 * 1024 * 1024)
+#endif
+
 typedef struct private_ha_socket_t private_ha_socket_t;
 
 /**
@@ -174,6 +181,8 @@ METHOD(ha_socket_t, pull, ha_message_t*,
  */
 static bool open_socket(private_ha_socket_t *this)
 {
+	int rcvbuf_size = 0;
+
 	this->fd = socket(this->local->get_family(this->local), SOCK_DGRAM, 0);
 	if (this->fd == -1)
 	{
@@ -189,6 +198,26 @@ static bool open_socket(private_ha_socket_t *this)
 		this->fd = -1;
 		return FALSE;
 	}
+
+	rcvbuf_size = lib->settings->get_int(lib->settings,
+										 "%s.plugins.ha.receive_buffer_size",
+										 HA_SOCKET_RCVBUF_DEFAULT, lib->ns);
+	if (rcvbuf_size)
+	{
+#ifdef SO_RCVBUFFORCE
+		if (setsockopt(this->fd, SOL_SOCKET, SO_RCVBUFFORCE, &rcvbuf_size,
+					   sizeof(rcvbuf_size)) == -1)
+#endif
+		{
+			if (setsockopt(this->fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf_size,
+						   sizeof(rcvbuf_size)) == -1)
+			{
+				DBG1(DBG_CFG, "failed to set receive buffer size to %d: %s",
+					 rcvbuf_size, strerror(errno));
+			}
+		}
+	}
+
 	if (connect(this->fd, this->remote->get_sockaddr(this->remote),
 				*this->remote->get_sockaddr_len(this->remote)) == -1)
 	{