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l2tp: dont play with skb->truesize 

Andrew Savchenko reported a DNS failure and we diagnosed that
some UDP sockets were unable to send more packets because their
sk_wmem_alloc was corrupted after a while (tx_queue column in
following trace)

$ cat /proc/net/udp
  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode ref pointer drops
...
  459: 00000000:0270 00000000:0000 07 00000000:00000000 00:00000000 00000000     0        0 4507 2 ffff88003d612380 0
  466: 00000000:0277 00000000:0000 07 00000000:00000000 00:00000000 00000000     0        0 4802 2 ffff88003d613180 0
  470: 076A070A:007B 00000000:0000 07 FFFF4600:00000000 00:00000000 00000000   123        0 5552 2 ffff880039974380 0
  470: 010213AC:007B 00000000:0000 07 00000000:00000000 00:00000000 00000000     0        0 4986 2 ffff88003dbd3180 0
  470: 010013AC:007B 00000000:0000 07 00000000:00000000 00:00000000 00000000     0        0 4985 2 ffff88003dbd2e00 0
  470: 00FCA8C0:007B 00000000:0000 07 FFFFFB00:00000000 00:00000000 00000000     0        0 4984 2 ffff88003dbd2a80 0
...

Playing with skb->truesize is tricky, especially when
skb is attached to a socket, as we can fool memory charging.

Just remove this code, its not worth trying to be ultra
precise in xmit path.

Reported-by: Andrew Savchenko <bircoph@gmail.com>
Tested-by: Andrew Savchenko <bircoph@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2013-02-07 14:00:34 +00:00 коммит произвёл David S. Miller
Родитель 586c31f3bf
Коммит 87c084a980
2 изменённых файлов: 0 добавлений и 12 удалений
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6
net/l2tp/l2tp_core.c
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@ -1168,8 +1168,6 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
struct udphdr *uh;
struct inet_sock *inet;
__wsum csum;
int old_headroom;
int new_headroom;
int headroom;
int uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
int udp_len;
@ -1181,16 +1179,12 @@ int l2tp_xmit_skb(struct l2tp_session *session, struct sk_buff *skb, int hdr_len
*/
headroom = NET_SKB_PAD + sizeof(struct iphdr) +
uhlen + hdr_len;
old_headroom = skb_headroom(skb);
if (skb_cow_head(skb, headroom)) {
kfree_skb(skb);
return NET_XMIT_DROP;
}
new_headroom = skb_headroom(skb);
skb_orphan(skb);
skb->truesize += new_headroom - old_headroom;
/* Setup L2TP header */
session->build_header(session, __skb_push(skb, hdr_len));

6
net/l2tp/l2tp_ppp.c
Просмотреть файл

@ -388,8 +388,6 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
struct l2tp_session *session;
struct l2tp_tunnel *tunnel;
struct pppol2tp_session *ps;
int old_headroom;
int new_headroom;
int uhlen, headroom;
if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
@ -408,7 +406,6 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
if (tunnel == NULL)
goto abort_put_sess;
old_headroom = skb_headroom(skb);
uhlen = (tunnel->encap == L2TP_ENCAPTYPE_UDP) ? sizeof(struct udphdr) : 0;
headroom = NET_SKB_PAD +
sizeof(struct iphdr) + /* IP header */
@ -418,9 +415,6 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
if (skb_cow_head(skb, headroom))
goto abort_put_sess_tun;
new_headroom = skb_headroom(skb);
skb->truesize += new_headroom - old_headroom;
/* Setup PPP header */
__skb_push(skb, sizeof(ppph));
skb->data[0] = ppph[0];