Re: [PATCH net-next v2 1/2] udp: Preserve UDP socket addresses on abort

[Kuniyuki Iwashima <kuniyu@google.com>]

From: Jordan Rife <jrife@google.com>
Date: Tue,  3 Mar 2026 17:01:02 +0000
> Currently, udp_abort() invokes __udp_disconnect() which clears out
> socket fields like inet_daddr and inet_dport. This makes fields like
> dst_ip4, dst_ip6, and dst_port useless inside cgroup/sock_release BPF
> hooks following an abort on a connected UDP socket, since they'll always
> equal zero. This differs from the behavior for TCP sockets where a
> cgroup/sock_release hook will see the address and port that the socket
> was connected to at the time it was aborted. This causes issues in
> Cilium where a sock_release hook is used to perform map maintenance when
> sockets are released, since Cilium actively destroys connected UDP
> sockets in some cases.

Just curious why Cilium does not unregister the socket just
after aborting it ?

At least Cilium should know the key at that moment.


> 
> Make the behavior consistent between TCP and UDP sockets by not clearing

This patch makes another inconsistency with TCP.

As you mentioned in the cover letter, before the patch, even if
aborted, a bound socket still reserves a port, but it does not now.

This might be surprising for non-reuseaddr/port sockets.


> out these fields in udp_abort(). Instead, just unhash the socket, mark
> its state as TCP_CLOSE, and preserve the state of the other fields.
> 
> Fixes: f5836749c9c0 ("bpf: Add BPF_CGROUP_INET_SOCK_RELEASE hook")
> Reported-by: Yusuke Suzuki <yusuke.suzuki@isovalent.com>
> Signed-off-by: Jordan Rife <jrife@google.com>
> ---
>  net/ipv4/udp.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index b96e47f1c8a2..01a0a0fbcd56 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -3247,7 +3247,9 @@ int udp_abort(struct sock *sk, int err)
>  
>  	sk->sk_err = err;
>  	sk_error_report(sk);
> -	__udp_disconnect(sk, 0);

How about passing another flag and avoid unwanted init only for
bpf iterator ?  This will need another layer of __udp_disconnect()
like ____udp_disconnect() (I'm not good at naming), or must make
sure the flag is never used in uAPI.



> +	sk->sk_state = TCP_CLOSE;
> +	sk->sk_prot->unhash(sk);
> +	sk_dst_reset(sk);
>  
>  out:
>  	if (!has_current_bpf_ctx())
> -- 
> 2.53.0.473.g4a7958ca14-goog
>