In 93515d53b1
"net: move vlan pop/push functions into common code"
skb_vlan_pop was moved from its private location in openvswitch to
skbuff common code.
In case skb has non hw-accel vlan tag, the original 'pop_vlan()' assured
that skb->len is sufficient (if skb->len < VLAN_ETH_HLEN then pop was
considered a no-op).
This validation was moved as is into the new common 'skb_vlan_pop'.
Alas, in its original location (openvswitch), there was a guarantee that
'data' points to the mac_header, therefore the 'skb->len < VLAN_ETH_HLEN'
condition made sense.
However there's no such guarantee in the generic 'skb_vlan_pop'.
For short packets received in rx path going through 'skb_vlan_pop',
this causes 'skb_vlan_pop' to fail pop-ing a valid vlan hdr (in the non
hw-accel case) or to fail moving next tag into hw-accel tag.
Remove the 'skb->len < VLAN_ETH_HLEN' condition entirely:
It is superfluous since inner '__skb_vlan_pop' already verifies there
are VLAN_ETH_HLEN writable bytes at the mac_header.
Note this presents a slight change to skb_vlan_pop() users:
In case total length is smaller than VLAN_ETH_HLEN, skb_vlan_pop() now
returns an error, as opposed to previous "no-op" behavior.
Existing callers (e.g. tc act vlan, ovs) usually drop the packet if
'skb_vlan_pop' fails.
Fixes: 93515d53b1 ("net: move vlan pop/push functions into common code")
Signed-off-by: Shmulik Ladkani <shmulik.ladk...@gmail.com>
Cc: Pravin Shelar <pshe...@ovn.org>
---
v3: Elaborate log message to explain the change presented to
'skb_vlan_pop' users for packets smaller than VLAN_ETH_HLEN
v2: Remove 'skb->len < VLAN_ETH_HLEN' condition entirely (instead of
testing skb->mac_len as was in v1), suggested by Pravin Shelar
net/core/skbuff.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7bf82a2..93d6c5c 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4564,9 +4564,8 @@ int skb_vlan_pop(struct sk_buff *skb)
if (likely(skb_vlan_tag_present(skb))) {
skb->vlan_tci = 0;
} else {
- if (unlikely((skb->protocol != htons(ETH_P_8021Q) &&
- skb->protocol != htons(ETH_P_8021AD)) ||
- skb->len < VLAN_ETH_HLEN))
+ if (unlikely(skb->protocol != htons(ETH_P_8021Q) &&
+ skb->protocol != htons(ETH_P_8021AD)))
return 0;
err = __skb_vlan_pop(skb, &vlan_tci);
@@ -4574,9 +4573,8 @@ int skb_vlan_pop(struct sk_buff *skb)
return err;
}
/* move next vlan tag to hw accel tag */
- if (likely((skb->protocol != htons(ETH_P_8021Q) &&
- skb->protocol != htons(ETH_P_8021AD)) ||
- skb->len < VLAN_ETH_HLEN))
+ if (likely(skb->protocol != htons(ETH_P_8021Q) &&
+ skb->protocol != htons(ETH_P_8021AD)))
return 0;
vlan_proto = skb->protocol;
--
1.9.1
