From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id CA8BB51E43C; Fri, 18 Sep 2026 18:38:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789756732; cv=none; b=fPGOLcBHaKx5Sy/ZvmppiO83l9WqFF3lUy+DFP8YizyamEn2eXlQbQt9KIlfspHaTTw0+4fsCxZpeEErZOWUOhjndmFWjXGc5w4mc+oeCJOOc2K+tDY+7Efbu8rcoN1gr+8kjPMEJrFXMTueEP6zztezhzXFRROCoN21Lsoe2+A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789756732; c=relaxed/simple; bh=fbWZZc8WwHlYza1PP7pAIgFAufWY3zIAyOEtVmk/sho=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=ivDCiiGNnE/yJbc3PKQaikMt1yQbUY/TZNbZKGJ61UYNaxgY4ot8INXAgtTh0hsX3vZMZAcm3c8RrNtziowMKL0I/YDVinO3l0nj0XveHDUJTXup470f+MMOZowLy3f6GQ4XMh4fTgiauMToNiJjKnnTv/bON7FBHwy7+7kW8Fc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Xkj4drDw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Xkj4drDw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB89C1F0089A; Fri, 18 Sep 2026 18:38:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789756725; bh=2y7axseDLzTxuDDQ3sumIb+ws2cPPLcPH4O+iaVMq0Y=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=Xkj4drDw7PqDHbi8VYzXRWluum2lNGqg6HwYdY4Et1WY/ixopopuckEzuFxoFYkuy wF8ms12VczQfoaHJp5IXT4/DM3vcAvc/VWG5Nef3bj48kzV4rnLeVJygFI1zN8A3HX iLZGs0J6Yuk5o9ZpcOAuSqZBOUjM/CFCY34q5ov6HCIz7r4KfhBJ+oF5jMtNlKpRfb Ynyx3tQ2yr6NcK3rd8vpvFhI3zHY35u+IUUbqytOpUhp6/xYeeSZQ3Ajh+dATUU0Ap ZGP0KPDETIswKxGvtWkiO1e8Q+OQOdTTQoxw0/uZ1dCHon1H2sYEpOAt19ma2WIQSC dzznARva2Uo0g== From: "Matthieu Baerts (NGI0)" Date: Fri, 18 Sep 2026 20:38:27 +0200 Subject: [PATCH net-next 3/4] mptcp: propagate RECVERR sockopts to subflows Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260918-net-next-mptcp-msg_errqueue-v1-3-dd77e1738248@kernel.org> References: <20260918-net-next-mptcp-msg_errqueue-v1-0-dd77e1738248@kernel.org> In-Reply-To: <20260918-net-next-mptcp-msg_errqueue-v1-0-dd77e1738248@kernel.org> To: Mat Martineau , Geliang Tang , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netdev@vger.kernel.org, mptcp@lists.linux.dev, linux-kernel@vger.kernel.org, "Matthieu Baerts (NGI0)" , David Carlier X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=7716; i=matttbe@kernel.org; h=from:subject:message-id; bh=ZV6SJUXmelrp3RjG7TZg+4EZ/ra6RMfmhMZOXd3tH80=; b=owGbwMvMwCVWo/Th0Gd3rumMp9WSGLLWtmpNXKFbU7v0LENczPHfZ7lq7ihkLZsn3cr30aRyq sSUSo39HaUsDGJcDLJiiizSbZH5M59X8ZZ4+VnAzGFlAhnCwMUpABOZ94uRoVXHtUpi3bqreo3T 2YSfRHy+EGC5ZenlLwFX/M4ksoUkGjD8L4ibuO/vZ+/z5zcsMs5nPX0kIHPB3L2MVwMWdtcqrN6 xjBUA X-Developer-Key: i=matttbe@kernel.org; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 From: David Carlier Propagate IP_RECVERR/IP_RECVERR_RFC4884 and IPV6_RECVERR/IPV6_RECVERR_RFC4884 from the MPTCP socket to existing and future subflows. mptcp_setsockopt_recverr() snapshots optval into a local int, applies it to the parent socket via ip_setsockopt() / ipv6_setsockopt(), bumps msk->setsockopt_seq, and forwards to every subflow via mptcp_setsockopt_all_sf(). Newly-joining subflows pick up the four RECVERR bits through sync_socket_options() now that MPTCP_INET_FLAGS_MASK covers them. mptcp_setsockopt_all_sf() skips IPv4 subflows when called with SOL_IPV6: ipv6_setsockopt() on a sock with sk_family != AF_INET6 returns an error, which would abort the loop and leave the remaining subflows desynchronised. This branch was unreachable before this patch (the only caller was TCP_MAXSEG, family-agnostic); it becomes live with the new IPV6_RECVERR / IPV6_RECVERR_RFC4884 caller and the v4-subflow-on-AF_INET6-msk case (v4 MP_JOIN, or userspace PM grafting a v4 subflow onto a v6 msk). Assisted-by: Codex:gpt-5 Signed-off-by: David Carlier Acked-by: Paolo Abeni Signed-off-by: Matthieu Baerts (NGI0) --- net/mptcp/sockopt.c | 142 +++++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 119 insertions(+), 23 deletions(-) diff --git a/net/mptcp/sockopt.c b/net/mptcp/sockopt.c index 2ba56832587e..922f6ae5c80c 100644 --- a/net/mptcp/sockopt.c +++ b/net/mptcp/sockopt.c @@ -8,6 +8,7 @@ #include #include +#include #include #include #include @@ -19,7 +20,11 @@ #define MPTCP_INET_FLAGS_MASK \ (BIT(INET_FLAGS_TRANSPARENT) | \ BIT(INET_FLAGS_FREEBIND) | \ - BIT(INET_FLAGS_BIND_ADDRESS_NO_PORT)) + BIT(INET_FLAGS_BIND_ADDRESS_NO_PORT) | \ + BIT(INET_FLAGS_RECVERR) | \ + BIT(INET_FLAGS_RECVERR_RFC4884) | \ + BIT(INET_FLAGS_RECVERR6) | \ + BIT(INET_FLAGS_RECVERR6_RFC4884)) static struct sock *__mptcp_tcp_fallback(struct mptcp_sock *msk) { @@ -398,6 +403,86 @@ static int mptcp_setsockopt_sol_socket(struct mptcp_sock *msk, int optname, return -EOPNOTSUPP; } +static int mptcp_setsockopt_all_sf(struct mptcp_sock *msk, int level, + int optname, sockptr_t optval, + unsigned int optlen) +{ + struct mptcp_subflow_context *subflow; + int ret = 0; + + mptcp_for_each_subflow(msk, subflow) { + struct sock *ssk = mptcp_subflow_tcp_sock(subflow); + int err; + + /* SOL_IPV6 options on a v4 subflow (v4 MP_JOIN, or userspace PM + * grafting a v4 subflow onto an AF_INET6 msk) would otherwise + * abort the loop with -EAFNOSUPPORT from ipv6_setsockopt(). + */ + if (level == SOL_IPV6 && ssk->sk_family != AF_INET6) + continue; + + err = tcp_setsockopt(ssk, level, optname, optval, optlen); + if (err < 0 && ret == 0) + ret = err; + } + + if (!ret) + sockopt_seq_inc(msk); + + return ret; +} + +static int mptcp_setsockopt_recverr(struct mptcp_sock *msk, int level, + int optname, sockptr_t optval, + unsigned int optlen) +{ + struct sock *sk = (struct sock *)msk; + int val = 0, ret; + + /* Let ip_setsockopt() / ipv6_setsockopt() validate optval and optlen + * (so 1-byte boolean writes keep the same ABI as plain TCP) and update + * the parent's RECVERR bit. Re-read that bit under lock_sock() and + * push it to the subflows: concurrent setsockopt callers cannot leave + * parent and subflows desynchronized this way. + */ + if (level == SOL_IP) + ret = ip_setsockopt(sk, level, optname, optval, optlen); +#if IS_ENABLED(CONFIG_IPV6) + else if (level == SOL_IPV6) { + if (sk->sk_family != AF_INET6) + return -ENOPROTOOPT; + ret = ipv6_setsockopt(sk, level, optname, optval, optlen); + } +#endif + else + return -EOPNOTSUPP; + if (ret) + return ret; + + lock_sock(sk); + switch (optname) { + case IP_RECVERR: + val = inet_test_bit(RECVERR, sk); + break; + case IP_RECVERR_RFC4884: + val = inet_test_bit(RECVERR_RFC4884, sk); + break; +#if IS_ENABLED(CONFIG_IPV6) + case IPV6_RECVERR: + val = inet6_test_bit(RECVERR6, sk); + break; + case IPV6_RECVERR_RFC4884: + val = inet6_test_bit(RECVERR6_RFC4884, sk); + break; +#endif + } + + ret = mptcp_setsockopt_all_sf(msk, level, optname, + KERNEL_SOCKPTR(&val), sizeof(val)); + release_sock(sk); + return ret; +} + static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname, sockptr_t optval, unsigned int optlen) { @@ -440,6 +525,11 @@ static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname, release_sock(sk); break; + case IPV6_RECVERR: + case IPV6_RECVERR_RFC4884: + ret = mptcp_setsockopt_recverr(msk, SOL_IPV6, optname, optval, + optlen); + break; } return ret; @@ -785,6 +875,10 @@ static int mptcp_setsockopt_v4(struct mptcp_sock *msk, int optname, return mptcp_setsockopt_sol_ip_set(msk, optname, optval, optlen); case IP_TOS: return mptcp_setsockopt_v4_set_tos(msk, optname, optval, optlen); + case IP_RECVERR: + case IP_RECVERR_RFC4884: + return mptcp_setsockopt_recverr(msk, SOL_IP, optname, optval, + optlen); } return -EOPNOTSUPP; @@ -812,28 +906,6 @@ static int mptcp_setsockopt_first_sf_only(struct mptcp_sock *msk, int level, int return ret; } -static int mptcp_setsockopt_all_sf(struct mptcp_sock *msk, int level, - int optname, sockptr_t optval, - unsigned int optlen) -{ - struct mptcp_subflow_context *subflow; - int ret = 0; - - mptcp_for_each_subflow(msk, subflow) { - struct sock *ssk = mptcp_subflow_tcp_sock(subflow); - int err; - - err = tcp_setsockopt(ssk, level, optname, optval, optlen); - if (err < 0 && ret == 0) - ret = err; - } - - if (!ret) - sockopt_seq_inc(msk); - - return ret; -} - static int mptcp_setsockopt_sol_tcp(struct mptcp_sock *msk, int optname, sockptr_t optval, unsigned int optlen) { @@ -1478,6 +1550,12 @@ static int mptcp_getsockopt_v4(struct mptcp_sock *msk, int optname, case IP_LOCAL_PORT_RANGE: return mptcp_put_int_option(msk, optval, optlen, READ_ONCE(inet_sk(sk)->local_port_range)); + case IP_RECVERR: + return mptcp_put_int_option(msk, optval, optlen, + inet_test_bit(RECVERR, sk)); + case IP_RECVERR_RFC4884: + return mptcp_put_int_option(msk, optval, optlen, + inet_test_bit(RECVERR_RFC4884, sk)); } return -EOPNOTSUPP; @@ -1498,6 +1576,16 @@ static int mptcp_getsockopt_v6(struct mptcp_sock *msk, int optname, case IPV6_FREEBIND: return mptcp_put_int_option(msk, optval, optlen, inet_test_bit(FREEBIND, sk)); + case IPV6_RECVERR: + if (sk->sk_family != AF_INET6) + return -ENOPROTOOPT; + return mptcp_put_int_option(msk, optval, optlen, + inet6_test_bit(RECVERR6, sk)); + case IPV6_RECVERR_RFC4884: + if (sk->sk_family != AF_INET6) + return -ENOPROTOOPT; + return mptcp_put_int_option(msk, optval, optlen, + inet6_test_bit(RECVERR6_RFC4884, sk)); } return -EOPNOTSUPP; @@ -1606,6 +1694,14 @@ static void sync_socket_options(struct mptcp_sock *msk, struct sock *ssk) src = READ_ONCE(inet_sk(sk)->inet_flags); + /* RECVERR6 bits are only read on AF_INET6 sockets; copying them onto a + * v4 subflow is dead state and diverges from the SOL_IPV6 skip in + * mptcp_setsockopt_all_sf(). + */ + if (ssk->sk_family != AF_INET6) + mask &= ~(BIT(INET_FLAGS_RECVERR6) | + BIT(INET_FLAGS_RECVERR6_RFC4884)); + for_each_set_bit(b, &mask, BITS_PER_LONG) assign_bit(b, &inet_sk(ssk)->inet_flags, src & BIT(b)); -- 2.55.0