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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Davide Caratti <dcaratti@redhat.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 061/219] sched: act_csum: don't mangle TCP and
 UDP GSO packets
Thread-Topic: [PATCH AUTOSEL for 4.9 061/219] sched: act_csum: don't mangle
 TCP and UDP GSO packets
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Date:   Sat, 3 Mar 2018 22:28:31 +0000
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From: Davide Caratti <dcaratti@redhat.com>

[ Upstream commit add641e7dee31b36aee83412c29e39dd1f5e0c9c ]

after act_csum computes the checksum on skbs carrying GSO TCP/UDP packets,
subsequent segmentation fails because skb_needs_check(skb, true) returns
true. Because of that, skb_warn_bad_offload() is invoked and the following
message is displayed:

WARNING: CPU: 3 PID: 28 at net/core/dev.c:2553 skb_warn_bad_offload+0xf0/0x=
fd
<...>

  [<ffffffff8171f486>] skb_warn_bad_offload+0xf0/0xfd
  [<ffffffff8161304c>] __skb_gso_segment+0xec/0x110
  [<ffffffff8161340d>] validate_xmit_skb+0x12d/0x2b0
  [<ffffffff816135d2>] validate_xmit_skb_list+0x42/0x70
  [<ffffffff8163c560>] sch_direct_xmit+0xd0/0x1b0
  [<ffffffff8163c760>] __qdisc_run+0x120/0x270
  [<ffffffff81613b3d>] __dev_queue_xmit+0x23d/0x690
  [<ffffffff81613fa0>] dev_queue_xmit+0x10/0x20

Since GSO is able to compute checksum on individual segments of such skbs,
we can simply skip mangling the packet.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 net/sched/act_csum.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index e0defcef376d..24a0c66394a0 100644
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -180,6 +180,9 @@ static int tcf_csum_ipv4_tcp(struct sk_buff *skb, unsig=
ned int ihl,
 	struct tcphdr *tcph;
 	const struct iphdr *iph;
=20
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+		return 1;
+
 	tcph =3D tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
 	if (tcph =3D=3D NULL)
 		return 0;
@@ -201,6 +204,9 @@ static int tcf_csum_ipv6_tcp(struct sk_buff *skb, unsig=
ned int ihl,
 	struct tcphdr *tcph;
 	const struct ipv6hdr *ip6h;
=20
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+		return 1;
+
 	tcph =3D tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
 	if (tcph =3D=3D NULL)
 		return 0;
@@ -224,6 +230,9 @@ static int tcf_csum_ipv4_udp(struct sk_buff *skb, unsig=
ned int ihl,
 	const struct iphdr *iph;
 	u16 ul;
=20
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
+		return 1;
+
 	/*
 	 * Support both UDP and UDPLITE checksum algorithms, Don't use
 	 * udph->len to get the real length without any protocol check,
@@ -277,6 +286,9 @@ static int tcf_csum_ipv6_udp(struct sk_buff *skb, unsig=
ned int ihl,
 	const struct ipv6hdr *ip6h;
 	u16 ul;
=20
+	if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
+		return 1;
+
 	/*
 	 * Support both UDP and UDPLITE checksum algorithms, Don't use
 	 * udph->len to get the real length without any protocol check,
--=20
2.14.1