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-rw-r--r--net/rxrpc/ar-peer.c45
1 files changed, 44 insertions, 1 deletions
diff --git a/net/rxrpc/ar-peer.c b/net/rxrpc/ar-peer.c
index d399de4..ce08b78 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);
@@ -28,6 +29,47 @@ 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) {
+ kleave(" [route err %d]", ret);
+ return;
+ }
+
+ peer->if_mtu = dst_mtu(&rt->u.dst);
+ dst_release(&rt->u.dst);
+
+ kleave(" [if_mtu %u]", peer->if_mtu);
+}
+
+/*
* allocate a new peer
*/
static struct rxrpc_peer *rxrpc_alloc_peer(struct sockaddr_rxrpc *srx,
@@ -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);
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