l2tp: define l2tp_tunnel_dst_mtu()

Consolidate retrieval of tunnel's socket mtu in order to simplify
l2tp_eth and l2tp_ppp a bit.

Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 26 insertions, 21 deletions

diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index fa5ae9432d38..1ca39629031b 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -12,6 +12,9 @@
 #ifndef _L2TP_CORE_H_
 #define _L2TP_CORE_H_
 
+#include <net/dst.h>
+#include <net/sock.h>
+
 /* Just some random numbers */
 #define L2TP_TUNNEL_MAGIC       0x42114DDA
 #define L2TP_SESSION_MAGIC      0x0C04EB7D
@@ -268,6 +271,21 @@ static inline int l2tp_get_l2specific_len(struct l2tp_session *session)
         }
 }
 
+static inline u32 l2tp_tunnel_dst_mtu(const struct l2tp_tunnel *tunnel)
+{
+        struct dst_entry *dst;
+        u32 mtu;
+
+        dst = sk_dst_get(tunnel->sock);
+        if (!dst)
+                return 0;
+
+        mtu = dst_mtu(dst);
+        dst_release(dst);
+
+        return mtu;
+}
+
 #define l2tp_printk(ptr, type, func, fmt, ...)                          \
 do {                                                                    \
         if (((ptr)->debug) & (type))                                    \
diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c
index 5c366ecfa1cb..cfca5e63ae31 100644
--- a/net/l2tp/l2tp_eth.c
+++ b/net/l2tp/l2tp_eth.c
@@ -226,8 +226,8 @@ static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
                                 struct net_device *dev)
 {
         unsigned int overhead = 0;
-        struct dst_entry *dst;
         u32 l3_overhead = 0;
+        u32 mtu;
 
         /* if the encap is UDP, account for UDP header size */
         if (tunnel->encap == L2TP_ENCAPTYPE_UDP) {
@@ -256,15 +256,9 @@ static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
         overhead += session->hdr_len + ETH_HLEN + l3_overhead;
 
         /* If PMTU discovery was enabled, use discovered MTU on L2TP device */
-        dst = sk_dst_get(tunnel->sock);
-        if (dst) {
-                /* dst_mtu will use PMTU if found, else fallback to intf MTU */
-                u32 pmtu = dst_mtu(dst);
-
-                if (pmtu != 0)
-                        dev->mtu = pmtu;
-                dst_release(dst);
-        }
+        mtu = l2tp_tunnel_dst_mtu(tunnel);
+        if (mtu)
+                dev->mtu = mtu;
         session->mtu = dev->mtu - overhead;
         dev->mtu = session->mtu;
         dev->needed_headroom += session->hdr_len;
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 44cac66284a5..1c6da02f976a 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -93,7 +93,6 @@
 #include <linux/nsproxy.h>
 #include <net/net_namespace.h>
 #include <net/netns/generic.h>
-#include <net/dst.h>
 #include <net/ip.h>
 #include <net/udp.h>
 #include <net/xfrm.h>
@@ -554,7 +553,7 @@ static void pppol2tp_show(struct seq_file *m, void *arg)
 static void pppol2tp_session_init(struct l2tp_session *session)
 {
         struct pppol2tp_session *ps;
-        struct dst_entry *dst;
+        u32 mtu;
 
         session->recv_skb = pppol2tp_recv;
 #if IS_ENABLED(CONFIG_L2TP_DEBUGFS)
@@ -566,15 +565,9 @@ static void pppol2tp_session_init(struct l2tp_session *session)
         ps->owner = current->pid;
 
         /* If PMTU discovery was enabled, use the MTU that was discovered */
-        dst = sk_dst_get(session->tunnel->sock);
-        if (dst) {
-                u32 pmtu = dst_mtu(dst);
-
-                if (pmtu)
-                        session->mtu = pmtu - PPPOL2TP_HEADER_OVERHEAD;
-
-                dst_release(dst);
-        }
+        mtu = l2tp_tunnel_dst_mtu(session->tunnel);
+        if (mtu)
+                session->mtu = mtu - PPPOL2TP_HEADER_OVERHEAD;
 }
 
 struct l2tp_connect_info {