l2tp: give proper headroom in pppol2tp_xmit()
pppol2tp_xmit() calls skb_cow_head(skb, 2) before calling
l2tp_xmit_skb()
Then l2tp_xmit_skb() calls again skb_cow_head(skb, large_headroom)
This patchs changes the first skb_cow_head() call to supply the needed
headroom to make sure at most one (expensive) pskb_expand_head() is
done.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index f42cd09..8a90d75 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -395,6 +395,7 @@
struct pppol2tp_session *ps;
int old_headroom;
int new_headroom;
+ int uhlen, headroom;
if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
goto abort;
@@ -413,7 +414,13 @@
goto abort_put_sess;
old_headroom = skb_headroom(skb);
- if (skb_cow_head(skb, sizeof(ppph)))
+ uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
+ headroom = NET_SKB_PAD +
+ sizeof(struct iphdr) + /* IP header */
+ uhlen + /* UDP header (if L2TP_ENCAPTYPE_UDP) */
+ session->hdr_len + /* L2TP header */
+ sizeof(ppph); /* PPP header */
+ if (skb_cow_head(skb, headroom))
goto abort_put_sess_tun;
new_headroom = skb_headroom(skb);