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[DCCP]: Fix skb->cb conflicts with IP 

dev_queue_xmit() and the other IP output functions expect to get a skb
with clear or properly initialized skb->cb. Unlike TCP and UDP, the
dccp_skb_cb doesn't contain a struct inet_skb_parm at the beginning,
so the DCCP-specific data is interpreted by the IP output functions.
This can cause false negatives for the conditional POST_ROUTING hook
invocation, making the packet bypass the hook.

Add a inet_skb_parm/inet6_skb_parm union to the beginning of
dccp_skb_cb to avoid clashes. Also add a BUILD_BUG_ON to make
sure it fits in the cb.

[ Combined with patch from Gerrit Renker to remove two now unnecessary
  memsets of IPCB(skb)->opt ]

Signed-off-by: Patrick McHardy <kaber@trash.net>
Acked-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McHardy 2008-04-12 18:35:41 -07:00 committed by David S. Miller
parent ae1b6a31b1
commit 028b027524
4 changed files with 9 additions and 2 deletions
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6
net/dccp/dccp.h
View File

@ -325,6 +325,12 @@ static inline int dccp_bad_service_code(const struct sock *sk,
* This is used for transmission as well as for reception.
*/
struct dccp_skb_cb {
union {
struct inet_skb_parm h4;
#if defined(CONFIG_IPV6) || defined (CONFIG_IPV6_MODULE)
struct inet6_skb_parm h6;
#endif
} header;
__u8 dccpd_type:4;
__u8 dccpd_ccval:4;
__u8 dccpd_reset_code,

1
net/dccp/ipv4.c
View File

@ -489,7 +489,6 @@ static int dccp_v4_send_response(struct sock *sk, struct request_sock *req,
dh->dccph_checksum = dccp_v4_csum_finish(skb, ireq->loc_addr,
ireq->rmt_addr);
memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
err = ip_build_and_send_pkt(skb, sk, ireq->loc_addr,
ireq->rmt_addr,
ireq->opt);

1
net/dccp/output.c
View File

@ -126,7 +126,6 @@ static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
err = icsk->icsk_af_ops->queue_xmit(skb, 0);
return net_xmit_eval(err);
}

3
net/dccp/proto.c
View File

@ -1057,6 +1057,9 @@ static int __init dccp_init(void)
int ehash_order, bhash_order, i;
int rc = -ENOBUFS;
BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >
FIELD_SIZEOF(struct sk_buff, cb));
dccp_hashinfo.bind_bucket_cachep =
kmem_cache_create("dccp_bind_bucket",
sizeof(struct inet_bind_bucket), 0,