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tap: fix incorrect variable used for USO check in set_offload()

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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.

This has not worked since the beginning, so
commit 399e082764 ("driver/net/tun: Added features for USO.")

Signed-off-by: Rongguang Wei <weirongguang@kylinos.cn>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260807070914.112698-1-clementwei90@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Rongguang Wei
2026-08-07 15:09:14 +08:00
committed by Jakub Kicinski
parent 34b270e789
commit fac7973f00
1 changed files with 2 additions and 3 deletions
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5
drivers/net/tap.c
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@@ -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;
}
/* 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;