5.15-stable review patch. If anyone has any objections, please let me know.
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From: Jonas Gorski jonas.gorski@gmail.com
[ Upstream commit 3d18a84eddde169d6dbf3c72cc5358b988c347d0 ]
The internal switch on BCM63XX SoCs will unconditionally add 802.1Q VLAN tags on egress to CPU when 802.1Q mode is enabled. We do this unconditionally since commit ed409f3bbaa5 ("net: dsa: b53: Configure VLANs while not filtering").
This is fine for VLAN aware bridges, but for standalone ports and vlan unaware bridges this means all packets are tagged with the default VID, which is 0.
While the kernel will treat that like untagged, this can break userspace applications processing raw packets, expecting untagged traffic, like STP daemons.
This also breaks several bridge tests, where the tcpdump output then does not match the expected output anymore.
Since 0 isn't a valid VID, just strip out the VLAN tag if we encounter it, unless the priority field is set, since that would be a valid tag again.
Fixes: 964dbf186eaa ("net: dsa: tag_brcm: add support for legacy tags") Signed-off-by: Jonas Gorski jonas.gorski@gmail.com Reviewed-by: Vladimir Oltean olteanv@gmail.com Link: https://patch.msgid.link/20251027194621.133301-1-jonas.gorski@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/dsa/tag_brcm.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c index 3c681d174c58b..4c58219e50449 100644 --- a/net/dsa/tag_brcm.c +++ b/net/dsa/tag_brcm.c @@ -251,12 +251,14 @@ static struct sk_buff *brcm_leg_tag_rcv(struct sk_buff *skb, { int len = BRCM_LEG_TAG_LEN; int source_port; + __be16 *proto; u8 *brcm_tag;
if (unlikely(!pskb_may_pull(skb, BRCM_LEG_TAG_LEN + VLAN_HLEN))) return NULL;
brcm_tag = dsa_etype_header_pos_rx(skb); + proto = (__be16 *)(brcm_tag + BRCM_LEG_TAG_LEN);
source_port = brcm_tag[5] & BRCM_LEG_PORT_ID;
@@ -264,8 +266,12 @@ static struct sk_buff *brcm_leg_tag_rcv(struct sk_buff *skb, if (!skb->dev) return NULL;
- /* VLAN tag is added by BCM63xx internal switch */ - if (netdev_uses_dsa(skb->dev)) + /* The internal switch in BCM63XX SoCs always tags on egress on the CPU + * port. We use VID 0 internally for untagged traffic, so strip the tag + * if the TCI field is all 0, and keep it otherwise to also retain + * e.g. 802.1p tagged packets. + */ + if (proto[0] == htons(ETH_P_8021Q) && proto[1] == 0) len += VLAN_HLEN;
/* Remove Broadcom tag and update checksum */