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[34.66.65.137]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-6b1ce2916a8sm13636111eaf.10.2026.09.01.04.32.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2026 04:32:20 -0700 (PDT) Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id CEFE660D1F; Tue, 1 Sep 2026 11:32:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=marliere.net; s=dkim; t=1788262338; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding; bh=hEmWNrm2JJeYYsOZMUufG1GNwpjiBF7RXVW8N5KgjKA=; b=WQN2egFWZ83BoX6boVS3fAw8WgfZ0I6glPax5x/l5hbQkcOA9qdHlRmUwJG+L2QAXOWQ/0 2FrGxt1oEu7Ia50mWE2W6OkRNFR4u7NwYGZWibuoBTBgBodLpNhOh+acBmuZNsq08XE7NS 9YzPM0GoZPq7Jrjmk9spTbWqny69Dsy7LG7r4zLxoRafEci2SQTaJbhGSjG3vQmEvOX/Dw t01lxVeOUVkwGOVkURI8osV7fmMYjiTYntFQry4vfqf26fU3MtyoBYatP4FdwZfVDpZ4mk OAFOm1FLZlW8D08mPh3r93zq2KrgjxnD2PKfxR9g6ebAwRDb94DAQNznjeXx4A== From: =?utf-8?q?Ricardo_B=2E_Marli=C3=A8re_=28SUSE=29?= Date: Tue, 01 Sep 2026 08:31:58 -0300 Subject: [PATCH net] selftests/net: Fix flaky bind_wildcard due to ephemeral port race 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: quoted-printable Message-Id: <20260901-selftests-net-bind_wildcard_race-v1-1-880ddc7ed62e@marliere.net> X-B4-Tracking: v=1; b=H4sIAK23lmoC/yWN2wrCMBBEf6Xss8E0Qr38ikjZbLZ2pcaSjRco/ XcTfTzDzJkFlJOwwqlZIPFLVB6xQLtpgEaMVzYSCoOzrrNH2xrlacisWU3kbLzE0L9lCoQp9Am JDVnb7dEF2tkDFM2ceJDP7+IMZQOXf6hPf2PKVV5rHpWNTxhprFEpbu8oEdb1C+5nDyOkAAAA X-Change-ID: 20260901-selftests-net-bind_wildcard_race-c0067a2dc308 To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Shuah Khan Cc: netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, =?utf-8?q?Ricardo_B=2E_Marli=C3=A8re_=28SUSE=29?= X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=openssh-sha256; t=1788262332; l=2208; i=ricardo@marliere.net; h=from:subject:message-id; bh=NRVm+NpeqhDaHD1stYDATNicwntE7vF0BHXpPUPT4Ug=; b=U1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAgguRCc5X8/UX9M40lkMnr//aFGOhce x5ezt8MFNUFlqYAAAAGcGF0YXR0AAAAAAAAAAZzaGE1MTIAAABTAAAAC3NzaC1lZDI1NTE5AAAA QAQvMA+iXtgn9SGn6DViwidV1JIXPs63Piol0t0aGONt4f1I1seQ/5dbxTlA5gP59kodzeGuJvW Uyx2XB5WcnAE= X-Developer-Key: i=ricardo@marliere.net; a=openssh; fpr=SHA256:pzhe0fJpYLz+3cZ33FFPhIfaUElk9CXPFFXmalIH+1g X-Last-TLS-Session-Version: TLSv1.3 bind_wildcard picks an ephemeral port by binding fd[0] with port 0, reads it back with getsockname(), and then reuses that exact port number for the other addresses/families in fd[1..7]. This all happens in the default network namespace, so unrelated processes on the same host are drawing from the very same ephemeral port range (net.ipv4.ip_local_port_range) at the same time. Such a process can independently get assigned that exact port number on a different, non-conflicting address in the short window between fd[0]'s bind() and fd[1]'s, making fd[1]'s bind() fail with EADDRINUSE for reasons that have nothing to do with the wildcard-bind behavior under test, e.g.: # bind_wildcard.c:775:plain:Expected ret (-1) =3D=3D 0 (0) # plain: Test terminated by assertion not ok N bind_wildcard.v6_local_v4_local.plain Fix it the same way so_incoming_cpu.c, tcp_port_share.c and reuseport_dualstack.c already do: unshare into a fresh network namespace and bring lo up, so there is nobody else to race with for the port. Signed-off-by: Ricardo B. Marli=C3=A8re (SUSE) --- tools/testing/selftests/net/bind_wildcard.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/tools/testing/selftests/net/bind_wildcard.c b/tools/testing/se= lftests/net/bind_wildcard.c index 7d11548b2c61..be3298c791b2 100644 --- a/tools/testing/selftests/net/bind_wildcard.c +++ b/tools/testing/selftests/net/bind_wildcard.c @@ -1,6 +1,8 @@ // SPDX-License-Identifier: GPL-2.0 /* Copyright Amazon.com Inc. or its affiliates. */ =20 +#define _GNU_SOURCE +#include #include #include =20 @@ -716,6 +718,9 @@ static void setup_addr(FIXTURE_DATA(bind_wildcard) *sel= f, int i, =20 FIXTURE_SETUP(bind_wildcard) { + ASSERT_EQ(unshare(CLONE_NEWNET), 0); + ASSERT_EQ(system("ip link set lo up"), 0); + setup_addr(self, 0, variant->family[0], variant->addr[0]); setup_addr(self, 1, variant->family[1], variant->addr[1]); =20 --- base-commit: 1376afc7660bad2a1a5ee0876898312a486cf8bd change-id: 20260901-selftests-net-bind_wildcard_race-c0067a2dc308 Best regards, -- =20 Ricardo B. Marli=C3=A8re (SUSE)