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[35.245.46.111]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8ac5408d2b2sm7727067b3.37.2026.09.30.08.11.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Sep 2026 08:11:55 -0700 (PDT) Date: Wed, 30 Sep 2026 11:11:55 -0400 From: Willem de Bruijn To: Eric Dumazet , "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , David Ahern , Ido Schimmel , netdev@vger.kernel.org, edumazet@google.com, Eric Dumazet , Jiayuan Chen Message-ID: In-Reply-To: <20260930144018.1174068-2-edumazet@kernel.org> References: <20260930144018.1174068-1-edumazet@kernel.org> <20260930144018.1174068-2-edumazet@kernel.org> Subject: Re: [PATCH v2 net 1/2] ipv4: fix IP ID reuse in ip_select_ident_segs() Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Eric Dumazet wrote: > ip_select_ident_segs() must put the first of the @segs reserved IP IDs > in iph->id, as GSO assigns id, id + 1, ..., id + segs - 1 to segments. > > Commit f866fbc842de ("ipv4: fix data-races around inet->inet_id") > used atomic_add_return() for non-TCP sockets, which returns the first > ID of the next packet instead. Consecutive GSO packets can then reuse > IP IDs. > > SCTP GSO is affected. Other callers use segs == 1, and only see > a harmless off-by-one (UDP GSO has a separate, older issue). > > Use atomic_fetch_add() instead, like the TCP path. > > Fixes: f866fbc842de ("ipv4: fix data-races around inet->inet_id") > Signed-off-by: Eric Dumazet > Reviewed-by: Jiayuan Chen > Reviewed-by: David Ahern Reviewed-by: Willem de Bruijn