From: Geliang Tang Before commit c5c37af6ecad9 ("tcp: Convert do_tcp_sendpages() to use MSG_SPLICE_PAGES"), do_tcp_sendpages() did not call tcp_rate_check_app_limited() internally, so callers needed an explicit tcp_rate_check_app_limited() to cover it. That commit replaced do_tcp_sendpages() with direct tcp_sendmsg_locked() calls, which perform the check on every path that queues data. The outer call became redundant but was left in place. The site changed here, tcp_bpf_push(), holds the socket lock and invokes tcp_sendmsg_locked() on every iteration. The early-return paths in tcp_sendmsg_locked() that skip tcp_rate_check_app_limited() -- the MSG_ZEROCOPY allocation failure and MSG_FASTOPEN branches -- return without queueing any MSG_SPLICE_PAGES data, so there is no functional consequence from omitting the outer check. A potential benefit of this change is that it facilitates future reuse of tcp_bpf_push() for sockmap support in protocols beyond TCP, such as MPTCP. Since tcp_rate_check_app_limited() is TCP-specific while sendmsg_locked() is a generic interface in struct proto_ops, this change allows us to switch to different protocols via sk->sk_socket->ops->sendmsg_locked() without carrying protocol-specific assumptions. Signed-off-by: Geliang Tang --- Note: This patch was originally part of my ongoing "MPTCP sockmap support" series [1] (patch 5). Matthieu suggested converting it to a fix and sending it directly to netdev. Removing the redundant tcp_rate_check_app_limited() call benefits my subsequent MPTCP work: in patch 3 of that series, I implement an MPTCP-specific mptcp_rate_check_app_limited() function and call it in mptcp_sendmsg_locked(). This allows me to reuse tcp_bpf_push() by simply replacing tcp_sendmsg_locked() with sk->sk_socket->ops->sendmsg_locked(), without carrying protocol-specific assumptions. v3: - send this patch separately to bpf as Jakub suggested. - update the commit log as bot+bpf-ci suggested. v2: - drop the "Fixes" tags and update the prefixes and commit logs as Jiayuan suggested. - https://patchwork.kernel.org/project/netdevbpf/cover/cover.1789469930.git.tanggeliang@kylinos.cn/ v1: - https://patchwork.kernel.org/project/netdevbpf/cover/cover.1789368148.git.tanggeliang@kylinos.cn/ [1] MPTCP sockmap support https://lore.kernel.org/mptcp/b5f9e8d7-b738-1df6-3b5e-1d54cbbc663c@gmail.com/T/#t --- net/ipv4/tcp_bpf.c | 1 - 1 file changed, 1 deletion(-) diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c index 2e234d155b5e..d5fcf3ce4861 100644 --- a/net/ipv4/tcp_bpf.c +++ b/net/ipv4/tcp_bpf.c @@ -108,7 +108,6 @@ static int tcp_bpf_push(struct sock *sk, struct sk_msg *msg, u32 apply_bytes, off = sge->offset; page = sg_page(sge); - tcp_rate_check_app_limited(sk); retry: msghdr.msg_flags = flags | MSG_SPLICE_PAGES; has_tx_ulp = tls_sw_has_ctx_tx(sk); -- 2.53.0