From: John Fastabend <john.fastabend@gmail.com>
To: mptcp@lists.linux.dev,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
bpf@vger.kernel.org, netdev@vger.kernel.org
Cc: daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com,
memxor@gmail.com, john.fastabend@gmail.com, jakub@cloudflare.com,
jiayuan.chen@linux.dev, davem@davemloft.net, edumazet@kernel.org,
kuba@kernel.org, pabeni@redhat.com, horms@kernel.org,
kuniyu@google.com, willemb@google.com, matttbe@kernel.org,
mptcp@lists.linux.dev, mason@kernel.org, josef@toxicpanda.com
Subject: Re: [PATCH bpf v2 04/15] bpf, sockmap: Subtract all dropped bytes from the return value
Date: Mon, 02 Nov 2026 12:12:46 -0700 [thread overview]
Message-ID: <tnw2q0.1tgt7zq8oeb0@gmail.com> (raw)
In-Reply-To: <20261102072112.4160195-5-alexei.starovoitov@gmail.com>
On Mon, 02 Nov 2026 00:21, Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote:
>From: Alexei Starovoitov <ast@kernel.org>
>
>When an sk_msg prog returns SK_DROP, tcp_bpf_send_verdict() frees the full
>message. It then subtracts tosend bytes from *copied, the return value of
>sendmsg(). But tosend is the number of bytes that the verdict applies to.
>After bpf_msg_apply_bytes() tosend can be less than the message size. Then
>sendmsg() reports dropped bytes as sent.
>
>Subtract the number of bytes that sk_msg_free() frees. After an error the
>SK_PASS branch already does this. The SK_REDIRECT branch does the same if
>the message is not the cork. Nothing changes when tosend is equal to the
>message size. Otherwise sendmsg() now returns -EACCES if it sends nothing.
>
>Fixes: ca70b8baf2bd ("tcp_bpf: Fix the sk_mem_uncharge logic in tcp_bpf_sendmsg")
>Signed-off-by: Alexei Starovoitov <ast@kernel.org>
>---
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
next prev parent reply other threads:[~2026-11-02 19:13 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-02 7:20 [PATCH bpf v2 00/15] bpf, sockmap: Fixes for verdicts, redirects, corks and recvmsg() Alexei Starovoitov
2026-11-02 7:20 ` [PATCH bpf v2 01/15] bpf, sockmap: Write sg.start when recvmsg() faults Alexei Starovoitov
2026-11-02 8:32 ` Jiayuan Chen
2026-11-02 7:20 ` [PATCH bpf v2 02/15] bpf, sockmap: Don't let an SK_DROP verdict stick Alexei Starovoitov
2026-11-02 8:45 ` Jiayuan Chen
2026-11-02 18:47 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 03/15] bpf, sockmap: Don't let an SK_PASS verdict cover the next message Alexei Starovoitov
2026-11-02 18:51 ` John Fastabend
2026-11-02 22:44 ` Alexei Starovoitov
2026-11-02 7:21 ` [PATCH bpf v2 04/15] bpf, sockmap: Subtract all dropped bytes from the return value Alexei Starovoitov
2026-11-02 11:19 ` Jiayuan Chen
2026-11-02 19:12 ` John Fastabend [this message]
2026-11-02 7:21 ` [PATCH bpf v2 05/15] bpf, sockmap: Clear the resume state of a stopped psock Alexei Starovoitov
2026-11-02 11:40 ` Jiayuan Chen
2026-11-02 19:16 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 06/15] bpf, sockmap: Give no progs to a TCP listener Alexei Starovoitov
2026-11-02 12:00 ` Jiayuan Chen
2026-11-02 19:31 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 07/15] bpf, sockmap: Check the target of an egress redirect before each send Alexei Starovoitov
2026-11-02 12:32 ` Jiayuan Chen
2026-11-02 16:18 ` Alexei Starovoitov
2026-11-02 19:36 ` John Fastabend
2026-11-02 7:21 ` [PATCH bpf v2 08/15] net: Leave sk_stream_wait_memory() once the socket is dead Alexei Starovoitov
2026-11-02 12:54 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 09/15] bpf, sockmap: Check the TCP state in recvmsg() Alexei Starovoitov
2026-11-02 15:15 ` Jiayuan Chen
2026-11-02 16:57 ` Matthieu Baerts
2026-11-02 7:21 ` [PATCH bpf v2 10/15] bpf, sockmap: Reset the copy position when corking Alexei Starovoitov
2026-11-03 1:39 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 11/15] bpf, sockmap: Don't copy 0 bytes into a full cork Alexei Starovoitov
2026-11-03 1:41 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 12/15] bpf, sockmap: Clear the redirect target before the sk_msg prog runs Alexei Starovoitov
2026-11-03 1:58 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 13/15] bpf, sockmap: Check that the redirected message is the cork Alexei Starovoitov
2026-11-03 2:07 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 14/15] bpf, sockmap: Keep the rest of the cork after a redirect Alexei Starovoitov
2026-11-03 2:25 ` Jiayuan Chen
2026-11-02 7:21 ` [PATCH bpf v2 15/15] bpf, sockmap: Clear the end mark of elements added by push and pop Alexei Starovoitov
2026-11-03 2:51 ` Jiayuan Chen
2026-11-02 9:29 ` [PATCH bpf v2 00/15] bpf, sockmap: Fixes for verdicts, redirects, corks and recvmsg() MPTCP CI
2026-11-02 20:11 ` John Fastabend
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