Commit 426ca15c7f6c for kernel

commit 426ca15c7f6cb6562a081341ca88893a50c59fa2
Author: Jibin Zhang <jibin.zhang@mediatek.com>
Date:   Mon Jan 26 23:21:11 2026 +0800

    net: fix segmentation of forwarding fraglist GRO

    This patch enhances GSO segment handling by properly checking
    the SKB_GSO_DODGY flag for frag_list GSO packets, addressing
    low throughput issues observed when a station accesses IPv4
    servers via hotspots with an IPv6-only upstream interface.

    Specifically, it fixes a bug in GSO segmentation when forwarding
    GRO packets containing a frag_list. The function skb_segment_list
    cannot correctly process GRO skbs that have been converted by XLAT,
    since XLAT only translates the header of the head skb. Consequently,
    skbs in the frag_list may remain untranslated, resulting in protocol
    inconsistencies and reduced throughput.

    To address this, the patch explicitly sets the SKB_GSO_DODGY flag
    for GSO packets in XLAT's IPv4/IPv6 protocol translation helpers
    (bpf_skb_proto_4_to_6 and bpf_skb_proto_6_to_4). This marks GSO
    packets as potentially modified after protocol translation. As a
    result, GSO segmentation will avoid using skb_segment_list and
    instead falls back to skb_segment for packets with the SKB_GSO_DODGY
    flag. This ensures that only safe and fully translated frag_list
    packets are processed by skb_segment_list, resolving protocol
    inconsistencies and improving throughput when forwarding GRO packets
    converted by XLAT.

    Signed-off-by: Jibin Zhang <jibin.zhang@mediatek.com>
    Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.")
    Cc: stable@vger.kernel.org
    Link: https://patch.msgid.link/20260126152114.1211-1-jibin.zhang@mediatek.com
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/net/core/filter.c b/net/core/filter.c
index 616e0520a0bb..bcd73d9bd764 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3353,6 +3353,7 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb)
 			shinfo->gso_type &= ~SKB_GSO_TCPV4;
 			shinfo->gso_type |=  SKB_GSO_TCPV6;
 		}
+		shinfo->gso_type |=  SKB_GSO_DODGY;
 	}

 	bpf_skb_change_protocol(skb, ETH_P_IPV6);
@@ -3383,6 +3384,7 @@ static int bpf_skb_proto_6_to_4(struct sk_buff *skb)
 			shinfo->gso_type &= ~SKB_GSO_TCPV6;
 			shinfo->gso_type |=  SKB_GSO_TCPV4;
 		}
+		shinfo->gso_type |=  SKB_GSO_DODGY;
 	}

 	bpf_skb_change_protocol(skb, ETH_P_IP);
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index fdda18b1abda..942a948f1a31 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -107,7 +107,8 @@ static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
 	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
 		struct tcphdr *th = tcp_hdr(skb);

-		if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size)
+		if ((skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size) &&
+		    !(skb_shinfo(skb)->gso_type & SKB_GSO_DODGY))
 			return __tcp4_gso_segment_list(skb, features);

 		skb->ip_summed = CHECKSUM_NONE;
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 19d0b5b09ffa..589456bd8b5f 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -514,7 +514,8 @@ struct sk_buff *__udp_gso_segment(struct sk_buff *gso_skb,

 	if (skb_shinfo(gso_skb)->gso_type & SKB_GSO_FRAGLIST) {
 		 /* Detect modified geometry and pass those to skb_segment. */
-		if (skb_pagelen(gso_skb) - sizeof(*uh) == skb_shinfo(gso_skb)->gso_size)
+		if ((skb_pagelen(gso_skb) - sizeof(*uh) == skb_shinfo(gso_skb)->gso_size) &&
+		    !(skb_shinfo(gso_skb)->gso_type & SKB_GSO_DODGY))
 			return __udp_gso_segment_list(gso_skb, features, is_ipv6);

 		ret = __skb_linearize(gso_skb);
diff --git a/net/ipv6/tcpv6_offload.c b/net/ipv6/tcpv6_offload.c
index effeba58630b..5670d32c27f8 100644
--- a/net/ipv6/tcpv6_offload.c
+++ b/net/ipv6/tcpv6_offload.c
@@ -170,7 +170,8 @@ static struct sk_buff *tcp6_gso_segment(struct sk_buff *skb,
 	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
 		struct tcphdr *th = tcp_hdr(skb);

-		if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size)
+		if ((skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size) &&
+		    !(skb_shinfo(skb)->gso_type & SKB_GSO_DODGY))
 			return __tcp6_gso_segment_list(skb, features);

 		skb->ip_summed = CHECKSUM_NONE;