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[34.48.4.250]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-66acae63149sm3163693d50.11.2026.08.08.08.39.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 08 Aug 2026 08:39:03 -0700 (PDT) Date: Sat, 08 Aug 2026 11:39:02 -0400 From: Willem de Bruijn To: Rongguang Wei , willemdebruijn.kernel@gmail.com, kuba@kernel.org, jasowangio@gmail.com, andrew+netdev@lunn.ch Cc: netdev@vger.kernel.org, Rongguang Wei , Willem de Bruijn Message-ID: In-Reply-To: <20260807070914.112698-1-clementwei90@163.com> References: <20260807070914.112698-1-clementwei90@163.com> Subject: Re: [PATCH net v2] tap: fix incorrect variable used for USO check in set_offload() 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 Rongguang Wei wrote: > From: Rongguang Wei > > The USO features in set_offload() incorrectly uses feature_mask and > features argument. > > The USO feature was written to the local features variable instead of > feature_mask. All other offload bits (TSO, TSO_ECN) are stored in > feature_mask which becomes tap->tap_features and is used by > tap_handle_frame() for GSO segmentation. Without NETIF_F_GSO_UDP_L4 > in tap->tap_features, making USO on tap effectively non-functional. > > Keeping the USO handling inside the TUN_F_CSUM block avoids enabling > GRO/LRO when userspace requests USO without CSUM. > > Fixes: 399e0827642f ("driver/net/tun: Added features for USO.") > Signed-off-by: Rongguang Wei > Reviewed-by: Willem de Bruijn Reviewed-by: Willem de Bruijn Substantially changed patch, please don't keep Reviewed-by tags across non-trivial changes. That said, I do agree, so adding it again. > --- > v2: Fix more incorrect variable in USO check. > https://lore.kernel.org/netdev/20260806163949.2807698-1-kuba@kernel.org/ > v1: https://lore.kernel.org/netdev/20260805072121.117472-1-clementwei90@163.com/ > --- > drivers/net/tap.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/tap.c b/drivers/net/tap.c > index 5d2d34d24ce8..d4ca2fee538b 100644 > --- a/drivers/net/tap.c > +++ b/drivers/net/tap.c > @@ -883,7 +883,7 @@ static int set_offload(struct tap_queue *q, unsigned long arg) > > /* TODO: for now USO4 and USO6 should work simultaneously */ > if ((arg & (TUN_F_USO4 | TUN_F_USO6)) == (TUN_F_USO4 | TUN_F_USO6)) > - features |= NETIF_F_GSO_UDP_L4; > + feature_mask |= NETIF_F_GSO_UDP_L4; Drivers/net/tun seems to have this same issue. Do you want to take a look or shall I? > } > > /* tun/tap driver inverts the usage for TSO offloads, where > @@ -894,8 +894,7 @@ static int set_offload(struct tap_queue *q, unsigned long arg) > * When user space turns off TSO, we turn off GSO/LRO so that > * user-space will not receive TSO frames. > */ > - if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6) || > - (feature_mask & (TUN_F_USO4 | TUN_F_USO6)) == (TUN_F_USO4 | TUN_F_USO6)) > + if (feature_mask & (NETIF_F_TSO | NETIF_F_TSO6 | NETIF_F_GSO_UDP_L4)) > features |= RX_OFFLOADS; > else > features &= ~RX_OFFLOADS;