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>
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 06389d5..2ac884d 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1168,8 +1168,6 @@
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 @@
*/
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));
diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 286366e..716605c 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -388,8 +388,6 @@
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 @@
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 @@
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];