[PATCH bpf v2] bpf, sockmap, udp: sk_prot needs inuse_idx set for proc stats

[PATCH bpf v2] bpf, sockmap, udp: sk_prot needs inuse_idx set for proc stats

[Jakub Sitnicki]

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@gmail.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.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

Re: [PATCH bpf v2] bpf, sockmap, udp: sk_prot needs inuse_idx set for proc stats

[Cong Wang]

On Wed, Jul 14, 2021 at 8:47 AM Jakub Sitnicki <jakub@cloudflare.com> wrote:
>
> 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@gmail.com>
> Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>

Reviewed-by: Cong Wang <cong.wang@bytedance.com>

Thanks for the update!

Re: [PATCH bpf v2] bpf, sockmap, udp: sk_prot needs inuse_idx set for proc stats

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf.git (refs/heads/master):

On Wed, 14 Jul 2021 17:47:50 +0200 you wrote:
> 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.
> 
> [...]

Here is the summary with links:
  - [bpf,v2] bpf, sockmap, udp: sk_prot needs inuse_idx set for proc stats
    https://git.kernel.org/bpf/bpf/c/54ea2f49fd94

You are awesome, thank you!
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