X-Git-Url: https://git.karo-electronics.de/?a=blobdiff_plain;f=net%2Frxrpc%2Far-peer.c;h=90fa107a8af99bc82fa7a6fd5a28d13885c121a0;hb=160acc2e899f26356bde92bc257253b7ca78f0c3;hp=d399de4a7fe2b98cdbe3011868181a703d3e2d50;hpb=15c54033964a943de7b0763efd3bd0ede7326395;p=karo-tx-linux.git

diff --git a/net/rxrpc/ar-peer.c b/net/rxrpc/ar-peer.c
index d399de4a7fe2..90fa107a8af9 100644
--- a/net/rxrpc/ar-peer.c
+++ b/net/rxrpc/ar-peer.c
@@ -19,6 +19,7 @@
 #include <net/sock.h>
 #include <net/af_rxrpc.h>
 #include <net/ip.h>
+#include <net/route.h>
 #include "ar-internal.h"
 
 static LIST_HEAD(rxrpc_peers);
@@ -27,6 +28,47 @@ static DECLARE_WAIT_QUEUE_HEAD(rxrpc_peer_wq);
 
 static void rxrpc_destroy_peer(struct work_struct *work);
 
+/*
+ * assess the MTU size for the network interface through which this peer is
+ * reached
+ */
+static void rxrpc_assess_MTU_size(struct rxrpc_peer *peer)
+{
+	struct rtable *rt;
+	struct flowi fl;
+	int ret;
+
+	peer->if_mtu = 1500;
+
+	memset(&fl, 0, sizeof(fl));
+
+	switch (peer->srx.transport.family) {
+	case AF_INET:
+		fl.oif = 0;
+		fl.proto = IPPROTO_UDP,
+		fl.nl_u.ip4_u.saddr = 0;
+		fl.nl_u.ip4_u.daddr = peer->srx.transport.sin.sin_addr.s_addr;
+		fl.nl_u.ip4_u.tos = 0;
+		/* assume AFS.CM talking to AFS.FS */
+		fl.uli_u.ports.sport = htons(7001);
+		fl.uli_u.ports.dport = htons(7000);
+		break;
+	default:
+		BUG();
+	}
+
+	ret = ip_route_output_key(&rt, &fl);
+	if (ret < 0) {
+		_leave(" [route err %d]", ret);
+		return;
+	}
+
+	peer->if_mtu = dst_mtu(&rt->u.dst);
+	dst_release(&rt->u.dst);
+
+	_leave(" [if_mtu %u]", peer->if_mtu);
+}
+
 /*
  * allocate a new peer
  */
@@ -47,7 +89,8 @@ static struct rxrpc_peer *rxrpc_alloc_peer(struct sockaddr_rxrpc *srx,
 		peer->debug_id = atomic_inc_return(&rxrpc_debug_id);
 		memcpy(&peer->srx, srx, sizeof(*srx));
 
-		peer->mtu = peer->if_mtu = 65535;
+		rxrpc_assess_MTU_size(peer);
+		peer->mtu = peer->if_mtu;
 
 		if (srx->transport.family == AF_INET) {
 			peer->hdrsize = sizeof(struct iphdr);