Re: [PATCH bpf 2/2] bpf: udp: Avoid calling reuseport's bpf_prog from udp_gro

From: Song Liu <songliubraving@fb.com>
To: Martin Lau <kafai@fb.com>
Cc: "bpf@vger.kernel.org" <bpf@vger.kernel.org>,
	Networking <netdev@vger.kernel.org>,
	Alexei Starovoitov <ast@fb.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	David Miller <davem@davemloft.net>,
	Kernel Team <Kernel-team@fb.com>,
	Tom Herbert <tom@herbertland.com>
Subject: Re: [PATCH bpf 2/2] bpf: udp: Avoid calling reuseport's bpf_prog from udp_gro
Date: Sat, 1 Jun 2019 23:54:46 +0000	[thread overview]
Message-ID: <AB1E485E-DAEE-49BD-BC86-1299C6830B7F@fb.com> (raw)
In-Reply-To: <20190531222913.2500781-1-kafai@fb.com>

> On May 31, 2019, at 3:29 PM, Martin KaFai Lau <kafai@fb.com> 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 <tom@herbertland.com>
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> ---
> 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,
> 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()?

> }
> 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
> 