From c56cae23c6b167acc68043c683c4573b80cbcc2c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
Date: Thu, 13 Sep 2018 16:43:07 +0200
Subject: [PATCH] gso_segment: Reset skb->mac_len after modifying network
header
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When splitting a GSO segment that consists of encapsulated packets, the
skb->mac_len of the segments can end up being set wrong, causing packet
drops in particular when using act_mirred and ifb interfaces in
combination with a qdisc that splits GSO packets.
This happens because at the time skb_segment() is called, network_header
will point to the inner header, throwing off the calculation in
skb_reset_mac_len(). The network_header is subsequently adjust by the
outer IP gso_segment handlers, but they don't set the mac_len.
Fix this by adding skb_reset_mac_len() calls to both the IPv4 and IPv6
gso_segment handlers, after they modify the network_header.
Many thanks to Eric Dumazet for his help in identifying the cause of
the bug.
Acked-by: Dave Taht <dave.taht@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/ipv4/af_inet.c | 1 +
net/ipv6/ip6_offload.c | 1 +
2 files changed, 2 insertions(+)
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 20fda8fb8ffda..1fbe2f815474c 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1377,6 +1377,7 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
if (encap)
skb_reset_inner_headers(skb);
skb->network_header = (u8 *)iph - skb->head;
+ skb_reset_mac_len(skb);
} while ((skb = skb->next));
out:
diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index 37ff4805b20c7..c7e495f120110 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -115,6 +115,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
payload_len = skb->len - nhoff - sizeof(*ipv6h);
ipv6h->payload_len = htons(payload_len);
skb->network_header = (u8 *)ipv6h - skb->head;
+ skb_reset_mac_len(skb);
if (udpfrag) {
int err = ip6_find_1stfragopt(skb, &prevhdr);
--
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