On Sat, Jun 01, 2019 at 04:54:46PM -0700, Song Liu wrote:

quoted

On May 31, 2019, at 3:29 PM, Martin KaFai Lau [off-list ref] wrote:

When the commit a6024562ffd7 ("udp: Add GRO functions to UDP socket")
added udp[46]_lib_lookup_skb to the udp_gro code path, it broke
the reuseport_select_sock() assumption that skb->data is pointing
to the transport header.

This patch follows an earlier __udp6_lib_err() fix by
passing a NULL skb to avoid calling the reuseport's bpf_prog.

Fixes: a6024562ffd7 ("udp: Add GRO functions to UDP socket")
Cc: Tom Herbert <redacted>
Signed-off-by: Martin KaFai Lau <redacted>
---
net/ipv4/udp.c | 6 +++++-
net/ipv6/udp.c | 2 +-
2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 8fb250ed53d4..85db0e3d7f3f 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c

@@ -503,7 +503,11 @@ static inline struct sock *__udp4_lib_lookup_skb(struct sk_buff *skb,

Note that this patch is changing the below "udp4_lib_lookup_skb()"
instead of the above "__udp4_lib_lookup_skb()".

quoted

struct sock *udp4_lib_lookup_skb(struct sk_buff *skb,
				 __be16 sport, __be16 dport)
{
-	return __udp4_lib_lookup_skb(skb, sport, dport, &udp_table);
+	const struct iphdr *iph = ip_hdr(skb);
+
+	return __udp4_lib_lookup(dev_net(skb->dev), iph->saddr, sport,
+				 iph->daddr, dport, inet_iif(skb),
+				 inet_sdif(skb), &udp_table, NULL);

I think we can now remove the last argument of __udp4_lib_lookup()?

The last arg of __udp4_lib_lookup() is skb.
__udp4_lib_lookup_skb(), which is not changed in this patch, is still
calling __udp4_lib_lookup() with a skb and the skb is used by the
reuseport's bpf_prog.  Hence, it cannot be removed.

quoted

}
EXPORT_SYMBOL_GPL(udp4_lib_lookup_skb);

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 133e6370f89c..4e52c37bb836 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c

@@ -243,7 +243,7 @@ struct sock *udp6_lib_lookup_skb(struct sk_buff *skb,

	return __udp6_lib_lookup(dev_net(skb->dev), &iph->saddr, sport,
				 &iph->daddr, dport, inet6_iif(skb),
-				 inet6_sdif(skb), &udp_table, skb);
+				 inet6_sdif(skb), &udp_table, NULL);
}
EXPORT_SYMBOL_GPL(udp6_lib_lookup_skb);

-- 
2.17.1