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authorVladimir Oltean <vladimir.oltean@nxp.com>2023-04-21 01:56:01 +0300
committerDavid S. Miller <davem@davemloft.net>2023-04-23 16:16:45 +0300
commit0bcf2e4aca6c29a07555b713f2fb461dc38d5977 (patch)
tree5cbeb17571c9738e1bcd2f33c02989b8e4e9eb42 /include/linux/if_vlan.h
parentf0a9d563064c3040a2d7b32317b37a6bcb1099b2 (diff)
downloadlinux-0bcf2e4aca6c29a07555b713f2fb461dc38d5977.tar.xz
net: dsa: tag_ocelot: call only the relevant portion of __skb_vlan_pop() on TX
ocelot_xmit_get_vlan_info() calls __skb_vlan_pop() as the most appropriate helper I could find which strips away a VLAN header. That's all I need it to do, but __skb_vlan_pop() has more logic, which will become incompatible with the future revert of commit 6d1ccff62780 ("net: reset mac header in dev_start_xmit()"). Namely, it performs a sanity check on skb_mac_header(), which will stop being set after the above revert, so it will return an error instead of removing the VLAN tag. ocelot_xmit_get_vlan_info() gets called in 2 circumstances: (1) the port is under a VLAN-aware bridge and the bridge sends VLAN-tagged packets (2) the port is under a VLAN-aware bridge and somebody else (an 8021q upper) sends VLAN-tagged packets (using a VID that isn't in the bridge vlan tables) In case (1), there is actually no bug to defend against, because br_dev_xmit() calls skb_reset_mac_header() and things continue to work. However, in case (2), illustrated using the commands below, it can be seen that our intervention is needed, since __skb_vlan_pop() complains: $ ip link add br0 type bridge vlan_filtering 1 && ip link set br0 up $ ip link set $eth master br0 && ip link set $eth up $ ip link add link $eth name $eth.100 type vlan id 100 && ip link set $eth.100 up $ ip addr add 192.168.100.1/24 dev $eth.100 I could fend off the checks in __skb_vlan_pop() with some skb_mac_header_was_set() calls, but seeing how few callers of __skb_vlan_pop() there are from TX paths, that seems rather unproductive. As an alternative solution, extract the bare minimum logic to strip a VLAN header, and move it to a new helper named vlan_remove_tag(), close to the definition of vlan_insert_tag(). Document it appropriately and make ocelot_xmit_get_vlan_info() call this smaller helper instead. Seeing that it doesn't appear illegal to test skb->protocol in the TX path, I guess it would be a good for vlan_remove_tag() to also absorb the vlan_set_encap_proto() function call. Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Reviewed-by: Simon Horman <simon.horman@corigine.com> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/if_vlan.h')
-rw-r--r--include/linux/if_vlan.h21
1 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 3698f2b391cd..0f40f379d75c 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -686,6 +686,27 @@ static inline void vlan_set_encap_proto(struct sk_buff *skb,
}
/**
+ * vlan_remove_tag - remove outer VLAN tag from payload
+ * @skb: skbuff to remove tag from
+ * @vlan_tci: buffer to store value
+ *
+ * Expects the skb to contain a VLAN tag in the payload, and to have skb->data
+ * pointing at the MAC header.
+ *
+ * Returns a new pointer to skb->data, or NULL on failure to pull.
+ */
+static inline void *vlan_remove_tag(struct sk_buff *skb, u16 *vlan_tci)
+{
+ struct vlan_hdr *vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN);
+
+ *vlan_tci = ntohs(vhdr->h_vlan_TCI);
+
+ memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN);
+ vlan_set_encap_proto(skb, vhdr);
+ return __skb_pull(skb, VLAN_HLEN);
+}
+
+/**
* skb_vlan_tagged - check if skb is vlan tagged.
* @skb: skbuff to query
*