netdev - [PATCH bpf v2] bpf, sockmap, udp: sk_prot needs inuse

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Message-Id: <20210714154750.528206-1-jakub@cloudflare.com>
Date:   Wed, 14 Jul 2021 17:47:50 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     John Fastabend <john.fastabend@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenz Bauer <lmb@...udflare.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH bpf v2] bpf, sockmap, udp: sk_prot needs inuse_idx set for proc stats

Proc socket stats use sk_prot->inuse_idx value to record inuse sock stats.
We currently do not set this correctly from sockmap side. The result is
reading sock stats '/proc/net/sockstat' gives incorrect values. The
socket counter is incremented correctly, but because we don't set the
counter correctly when we replace sk_prot we may omit the decrement.

To get the correct inuse_idx value move the core_initcall that initializes
the udp proto handlers to late_initcall. This way it is initialized after
UDP has the chance to assign the inuse_idx value from the register protocol
handler.

Fixes: edc6741cc660 ("bpf: Add sockmap hooks for UDP sockets")
Acked-by: John Fastabend <john.fastabend@...il.com>
Signed-off-by: Jakub Sitnicki <jakub@...udflare.com>
---

v2:
- Fixed "Fixes" tag (Cong Wang)

 net/ipv4/udp_bpf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/udp_bpf.c b/net/ipv4/udp_bpf.c
index 45b8782aec0c..9f5a5cdc38e6 100644
--- a/net/ipv4/udp_bpf.c
+++ b/net/ipv4/udp_bpf.c
@@ -134,7 +134,7 @@ static int __init udp_bpf_v4_build_proto(void)
 	udp_bpf_rebuild_protos(&udp_bpf_prots[UDP_BPF_IPV4], &udp_prot);
 	return 0;
 }
-core_initcall(udp_bpf_v4_build_proto);
+late_initcall(udp_bpf_v4_build_proto);

 int udp_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
 {
-- 
2.31.1