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 720C451614B; Mon, 21 Sep 2026 21:50:47 +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=1790027448; cv=none; b=sRzizSrdpY5idLq5V/k41WaRhcHiR8DpjQ/+OwIjW9tNy3iNV1yyJiZCspFnN2MAW7yjCe7keRangwFzIhSqJzoTjzbkGYMrYkPU9xQGvBEt2wRIH4mvIk2pCz6v+tnQ+j1+auF/Gn1W6OR4Kd+iLJg9Mb0epO8/ZMZnKaXodMY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790027448; c=relaxed/simple; bh=D71f7uILAyrvvvvFg//FqtUrM6J53vSeLJLumSknAOc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=mpyRrUg61EIDc9ybUwgipjiwxwj0fK2h63nhj7YKIf+zUCqVH5aXhvCNy43JxYEget6C73bLQys4vIy76ynPXOxtQ0pKUMExM9wgaGGqrWQFHZwJ21ykeiJ65/WUAp0CC2y+HZbZCPH+Zpr07aZFnV0auXE0S3w3+fuFw4XKWV0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TtYmyO8j; 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="TtYmyO8j" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B75011F000FF; Mon, 21 Sep 2026 21:50:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790027447; bh=HLip/4mebxRdBkh5E4jlcAdSH/jfbe3rHCsYtFhelbg=; h=From:To:Cc:Subject:Date; b=TtYmyO8j3KcTdifwzU+PrLpBm2q+hMv3htjFfZOBSvWhPmLnhm8cF+qJozcOG3NA8 S4ktO7f07yMdOYHNVFPZ/KTkyThgdvGXGSB71C9ihIvT2vLTJGoCG3oTGQ3gS52l0Q zwC5DopIop5pf/bnb0rXS9EkNYKlMIbbv1kjEapDUiE12pkVkpnrfSYoEUSuBk9QdW lkRoRFze9S1mvu3eT/x9XQr2+wP5ebUN1mzOsyXNY2Z66xQIVIPffJqXCsVRtCT/IO o9VnR70hF7gbG1zsTfi5o+O4LuDw9t9wPdWHUFjg0nG+twRw4oKCGDHkhKxEBNE/qO aAHvVrFVGwrLg== From: Allison Henderson To: netdev@vger.kernel.org, linux-rdma@vger.kernel.org, pabeni@redhat.com, edumazet@google.com, kuba@kernel.org, horms@kernel.org Cc: achender@kernel.org Subject: [PATCH net] net/rds: include the scope id in the sendmsg connection cache check Date: Mon, 21 Sep 2026 14:50:46 -0700 Message-Id: <20260921215046.174745-1-achender@kernel.org> X-Mailer: git-send-email 2.25.1 Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rds_sendmsg() reuses the connection cached in rs->rs_conn when its peer address and ToS match the request. The interface index is part of a connection's identity as well: rds_conn_create_outgoing() passes the request's scope_id down as dev_if, and rds_conn_lookup() compares c_dev_if, so sends to the same link-local address through two interfaces are two different connections. The cache-hit test never looked at it. A socket bound to a non-link-local address has rs_bound_scope_id 0, and the scope check at the top of rds_sendmsg() accepts any non-zero destination scope for such a socket. So after a send to fe80::x%ifA, a send to fe80::x%ifB hits the cached ifA connection and the datagram leaves through ifA, to whichever peer answers to that address there. Compare c_dev_if with the request's scope_id in the cache test, so that such a send takes the lookup path and finds, or creates, the ifB connection. Fixes: 1e2b44e78eea ("rds: Enable RDS IPv6 support") Assisted-by: Claude-Code:claude-fable-5 Signed-off-by: Allison Henderson --- net/rds/send.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/rds/send.c b/net/rds/send.c index 1afa981e5c06..38b9cc9e0d20 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -1342,7 +1342,8 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len) /* rds_conn_create has a spinlock that runs with IRQ off. * Caching the conn in the socket helps a lot. */ if (rs->rs_conn && ipv6_addr_equal(&rs->rs_conn->c_faddr, &daddr) && - rs->rs_tos == rs->rs_conn->c_tos) { + rs->rs_tos == rs->rs_conn->c_tos && + rs->rs_conn->c_dev_if == scope_id) { conn = rs->rs_conn; } else { conn = rds_conn_create_outgoing(sock_net(sock->sk), -- 2.25.1