netdev - [PATCH net v2 2/3] net/sched: act_pedit: fix 'ex munge' on network header in case of QinQ packet

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Message-Id: <463743998f21850eaeee3df73ee8e60ee7d2dfe6.1559237173.git.dcaratti@redhat.com>
Date:   Thu, 30 May 2019 20:03:42 +0200
From:   Davide Caratti <dcaratti@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Cc:     shuali@...hat.com, Eli Britstein <elibr@...lanox.com>
Subject: [PATCH net v2 2/3] net/sched: act_pedit: fix 'ex munge' on network header in case of QinQ packet

like it has been done in commit 2ecba2d1e45b ("net: sched: act_csum: Fix
csum calc for tagged packets"), also 'pedit' needs to adjust the network
offset when multiple tags are present in the packets: otherwise wrong IP
headers (but good checksums) can be observed with the following command:

 # tc filter add dev test0 parent ffff: protocol 802.1Q flower \
   vlan_ethtype ipv4 action \
   pedit ex munge ip ttl set 10 pipe \
   csum ip and icmp pipe \
   mirred egress redirect dev test1

Fixes: d8b9605d2697 ("net: sched: fix skb->protocol use in case of accelerated vlan path")
Reported-by: Li Shuang <shuali@...hat.com>
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
 net/sched/act_pedit.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/net/sched/act_pedit.c b/net/sched/act_pedit.c
index d790c02b9c6c..26e43d300160 100644
--- a/net/sched/act_pedit.c
+++ b/net/sched/act_pedit.c
@@ -277,9 +277,11 @@ static bool offset_valid(struct sk_buff *skb, int offset)
 }
 
 static int pedit_skb_hdr_offset(struct sk_buff *skb,
-				enum pedit_header_type htype, int *hoffset)
+				enum pedit_header_type htype, int *hoffset,
+				unsigned int *vlan_hdr_count)
 {
 	int ret = -EINVAL;
+	__be16 protocol;
 
 	switch (htype) {
 	case TCA_PEDIT_KEY_EX_HDR_TYPE_ETH:
@@ -291,8 +293,18 @@ static int pedit_skb_hdr_offset(struct sk_buff *skb,
 	case TCA_PEDIT_KEY_EX_HDR_TYPE_NETWORK:
 	case TCA_PEDIT_KEY_EX_HDR_TYPE_IP4:
 	case TCA_PEDIT_KEY_EX_HDR_TYPE_IP6:
-		*hoffset = skb_network_offset(skb);
-		ret = 0;
+		protocol = tc_skb_protocol(skb);
+again:
+		switch (protocol) {
+		case cpu_to_be16(ETH_P_8021AD): /* fall through */
+		case cpu_to_be16(ETH_P_8021Q):
+			if (!tc_skb_pull_vlans(skb, vlan_hdr_count, &protocol))
+				goto again;
+			return ret;
+		default:
+			*hoffset = skb_network_offset(skb);
+			ret = 0;
+		}
 		break;
 	case TCA_PEDIT_KEY_EX_HDR_TYPE_TCP:
 	case TCA_PEDIT_KEY_EX_HDR_TYPE_UDP:
@@ -313,6 +325,7 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 			 struct tcf_result *res)
 {
 	struct tcf_pedit *p = to_pedit(a);
+	unsigned int vlan_hdr_count = 0;
 	int i;
 
 	if (skb_unclone(skb, GFP_ATOMIC))
@@ -343,7 +356,8 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 				tkey_ex++;
 			}
 
-			rc = pedit_skb_hdr_offset(skb, htype, &hoffset);
+			rc = pedit_skb_hdr_offset(skb, htype, &hoffset,
+						  &vlan_hdr_count);
 			if (rc) {
 				pr_info("tc action pedit bad header type specified (0x%x)\n",
 					htype);
@@ -407,6 +421,10 @@ static int tcf_pedit_act(struct sk_buff *skb, const struct tc_action *a,
 bad:
 	p->tcf_qstats.overlimits++;
 done:
+	while (vlan_hdr_count--) {
+		skb_push(skb, VLAN_HLEN);
+		skb_reset_network_header(skb);
+	}
 	bstats_update(&p->tcf_bstats, skb);
 	spin_unlock(&p->tcf_lock);
 	return p->tcf_action;
-- 
2.20.1