[PATCH AUTOSEL for 4.9 061/219] sched: act_csum: don't mangle TCP and UDP GSO packets

Sasha Levin
2018-03-03T22:32:56Z

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+0xf0/0xfd
<...>

[<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, unsigned int ihl,
struct tcphdr *tcph;
const struct iphdr *iph;

+ if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
+ return 1;
+
tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
if (tcph == NULL)
return 0;
@@ -201,6 +204,9 @@ static int tcf_csum_ipv6_tcp(struct sk_buff *skb, unsigned int ihl,
struct tcphdr *tcph;
const struct ipv6hdr *ip6h;

+ if (skb_is_gso(skb) && skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
+ return 1;
+
tcph = tcf_csum_skb_nextlayer(skb, ihl, ipl, sizeof(*tcph));
if (tcph == NULL)
return 0;
@@ -224,6 +230,9 @@ static int tcf_csum_ipv4_udp(struct sk_buff *skb, unsigned int ihl,
const struct iphdr *iph;
u16 ul;

+ 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, unsigned int ihl,
const struct ipv6hdr *ip6h;
u16 ul;

+ 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,
--
2.14.1