[PATCH net v3] net/sched: act_ct: fix restore the qdisc_skb_cb after defrag

[PATCH net v3] net/sched: act_ct: fix restore the qdisc_skb_cb after defrag

[wenxu]

From: wenxu <wenxu@ucloud.cn>

The fragment packets do defrag in tcf_ct_handle_fragments
will clear the skb->cb which make the qdisc_skb_cb clear
too. So the qdsic_skb_cb should be store before defrag and
restore after that.
It also update the pkt_len after all the
fragments finish the defrag to one packet and make the
following actions counter correct.

Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")
Signed-off-by: wenxu <wenxu@ucloud.cn>
---
v2: update qdisc_skb_cb(skb)->pkt_len only for reassembled skbs
v3: fix uninit defrag data

 net/sched/act_ct.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/net/sched/act_ct.c b/net/sched/act_ct.c
index 67504ae..5928efb 100644
--- a/net/sched/act_ct.c
+++ b/net/sched/act_ct.c
@@ -673,9 +673,10 @@ static int tcf_ct_ipv6_is_fragment(struct sk_buff *skb, bool *frag)
 }
 
 static int tcf_ct_handle_fragments(struct net *net, struct sk_buff *skb,
-				   u8 family, u16 zone)
+				   u8 family, u16 zone, bool *defrag)
 {
 	enum ip_conntrack_info ctinfo;
+	struct qdisc_skb_cb cb;
 	struct nf_conn *ct;
 	int err = 0;
 	bool frag;
@@ -693,6 +694,7 @@ static int tcf_ct_handle_fragments(struct net *net, struct sk_buff *skb,
 		return err;
 
 	skb_get(skb);
+	cb = *qdisc_skb_cb(skb);
 
 	if (family == NFPROTO_IPV4) {
 		enum ip_defrag_users user = IP_DEFRAG_CONNTRACK_IN + zone;
@@ -703,6 +705,9 @@ static int tcf_ct_handle_fragments(struct net *net, struct sk_buff *skb,
 		local_bh_enable();
 		if (err && err != -EINPROGRESS)
 			goto out_free;
+
+		if (!err)
+			*defrag = true;
 	} else { /* NFPROTO_IPV6 */
 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)
 		enum ip6_defrag_users user = IP6_DEFRAG_CONNTRACK_IN + zone;
@@ -711,12 +716,16 @@ static int tcf_ct_handle_fragments(struct net *net, struct sk_buff *skb,
 		err = nf_ct_frag6_gather(net, skb, user);
 		if (err && err != -EINPROGRESS)
 			goto out_free;
+
+		if (!err)
+			*defrag = true;
 #else
 		err = -EOPNOTSUPP;
 		goto out_free;
 #endif
 	}
 
+	*qdisc_skb_cb(skb) = cb;
 	skb_clear_hash(skb);
 	skb->ignore_df = 1;
 	return err;
@@ -914,6 +923,7 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a,
 	int nh_ofs, err, retval;
 	struct tcf_ct_params *p;
 	bool skip_add = false;
+	bool defrag = false;
 	struct nf_conn *ct;
 	u8 family;
 
@@ -946,7 +956,7 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a,
 	 */
 	nh_ofs = skb_network_offset(skb);
 	skb_pull_rcsum(skb, nh_ofs);
-	err = tcf_ct_handle_fragments(net, skb, family, p->zone);
+	err = tcf_ct_handle_fragments(net, skb, family, p->zone, &defrag);
 	if (err == -EINPROGRESS) {
 		retval = TC_ACT_STOLEN;
 		goto out;
@@ -1014,6 +1024,8 @@ static int tcf_ct_act(struct sk_buff *skb, const struct tc_action *a,
 
 out:
 	tcf_action_update_bstats(&c->common, skb);
+	if (defrag)
+		qdisc_skb_cb(skb)->pkt_len = skb->len;
 	return retval;
 
 drop:
-- 
1.8.3.1

Re: [PATCH net v3] net/sched: act_ct: fix restore the qdisc_skb_cb after defrag

[David Miller]

From: wenxu@ucloud.cn
Date: Sun, 19 Jul 2020 20:30:37 +0800

> From: wenxu <wenxu@ucloud.cn>
> 
> The fragment packets do defrag in tcf_ct_handle_fragments
> will clear the skb->cb which make the qdisc_skb_cb clear
> too. So the qdsic_skb_cb should be store before defrag and
> restore after that.
> It also update the pkt_len after all the
> fragments finish the defrag to one packet and make the
> following actions counter correct.
> 
> Fixes: b57dc7c13ea9 ("net/sched: Introduce action ct")
> Signed-off-by: wenxu <wenxu@ucloud.cn>

Applied and queued up for -stable, thanks.