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l2tp: give proper headroom in pppol2tp_xmit()

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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>
This commit is contained in:
Eric Dumazet 2011-10-07 05:45:57 +00:00 committed by David S. Miller
parent bc416d9768
commit 09df57ca60
1 changed files with 8 additions and 1 deletions
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9
net/l2tp/l2tp_ppp.c
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@ -395,6 +395,7 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
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 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
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);