netdev - [PATCH net v2 1/3] net/sched: act_csum: pull all VLAN headers before checksumming

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Message-Id: <655b6508443c52f04be2b2fe9a6a7f2470b47ad1.1559237173.git.dcaratti@redhat.com>
Date:   Thu, 30 May 2019 20:03:41 +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 1/3] net/sched: act_csum: pull all VLAN headers before checksumming

TC 'csum' action needs to read the packets' ethertype. In case the value
is encoded in unstripped/nested VLAN headers, call pskb_may_pull() to be
sure that all tags are in the linear part of skb. While at it, move this
code in a helper function: other TC actions (like 'pedit' and 'skbedit')
might need to read the innermost ethertype.

Fixes: 2ecba2d1e45b ("net: sched: act_csum: Fix csum calc for tagged packets")
CC: Eli Britstein <elibr@...lanox.com>
CC: Li Shuang <shuali@...hat.com>
Suggested-by: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Davide Caratti <dcaratti@...hat.com>
---
 include/net/pkt_cls.h | 21 +++++++++++++++++++++
 net/sched/act_csum.c  | 14 ++------------
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
index 514e3c80ecc1..0215dfbda9ac 100644
--- a/include/net/pkt_cls.h
+++ b/include/net/pkt_cls.h
@@ -953,4 +953,25 @@ struct tc_root_qopt_offload {
 	bool ingress;
 };
 
+static inline int tc_skb_pull_vlans(struct sk_buff *skb,
+				    unsigned int *hdr_count,
+				    __be16 *proto)
+{
+	if (skb_vlan_tag_present(skb))
+		*proto = skb->protocol;
+
+	while (eth_type_vlan(*proto)) {
+		struct vlan_hdr *vlan;
+
+		if (unlikely(!pskb_may_pull(skb, VLAN_HLEN)))
+			return -ENOMEM;
+
+		vlan = (struct vlan_hdr *)skb->data;
+		*proto = vlan->h_vlan_encapsulated_proto;
+		skb_pull(skb, VLAN_HLEN);
+		skb_reset_network_header(skb);
+		(*hdr_count)++;
+	}
+	return 0;
+}
 #endif
diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index 14bb525e355e..e8308ddcae9d 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -574,7 +574,6 @@ static int tcf_csum_act(struct sk_buff *skb, const struct tc_action *a,
 			struct tcf_result *res)
 {
 	struct tcf_csum *p = to_tcf_csum(a);
-	bool orig_vlan_tag_present = false;
 	unsigned int vlan_hdr_count = 0;
 	struct tcf_csum_params *params;
 	u32 update_flags;
@@ -604,17 +603,8 @@ static int tcf_csum_act(struct sk_buff *skb, const struct tc_action *a,
 		break;
 	case cpu_to_be16(ETH_P_8021AD): /* fall through */
 	case cpu_to_be16(ETH_P_8021Q):
-		if (skb_vlan_tag_present(skb) && !orig_vlan_tag_present) {
-			protocol = skb->protocol;
-			orig_vlan_tag_present = true;
-		} else {
-			struct vlan_hdr *vlan = (struct vlan_hdr *)skb->data;
-
-			protocol = vlan->h_vlan_encapsulated_proto;
-			skb_pull(skb, VLAN_HLEN);
-			skb_reset_network_header(skb);
-			vlan_hdr_count++;
-		}
+		if (tc_skb_pull_vlans(skb, &vlan_hdr_count, &protocol))
+			goto drop;
 		goto again;
 	}
 
-- 
2.20.1