skb_vlan_pop/push were too generic, trying to support the cases where
skb->data is at mac header, and cases where skb->data is arbitrarily
elsewhere.
Supporting an arbitrary skb->data was complex and bogus:
- It failed to unwind skb->data to its original location post actual
pop/push.
(Also, semantic is not well defined for unwinding: If data was into
the eth header, need to use same offset from start; But if data was
at network header or beyond, need to adjust the original offset
according to the push/pull)
- It mangled the rcsum post actual push/pop, without taking into account
that the eth bytes might already have been pulled out of the csum.
Most callers (ovs, bpf) already had their skb->data at mac_header upon
invoking skb_vlan_pop/push.
Last caller that failed to do so (act_vlan) has been recently fixed.
Therefore, to simplify things, no longer support arbitrary skb->data
inputs for skb_vlan_pop/push().
skb->data is expected to be exactly at mac_header; WARN otherwise.
Signed-off-by: Shmulik Ladkani <shmulik.ladk...@gmail.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: Pravin Shelar <pshe...@ovn.org>
Cc: Jiri Pirko <j...@mellanox.com>
---
v3: Instead of correcting unwinding of skb->data in skb_vlan_pop/push,
just kill the support for arbitraray skb->data inputs, and assume
given skb->data always points at mac_header.
Fix act_vlan, the sole user not adehering to this assumption.
v2: Instead of reducing mac_len by 4 bytes, which was found incorrect,
fix the problem of wrong unwinding of 'skb->data'
net/core/skbuff.c | 37 ++++++++++++++++++++++---------------
1 file changed, 22 insertions(+), 15 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3864b4b68f..8c38263cdf 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4478,13 +4478,18 @@ EXPORT_SYMBOL(skb_ensure_writable);
static int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)
{
struct vlan_hdr *vhdr;
- unsigned int offset = skb->data - skb_mac_header(skb);
+ int offset = skb->data - skb_mac_header(skb);
int err;
- __skb_push(skb, offset);
+ if (WARN_ONCE(offset,
+ "__skb_vlan_pop got skb with skb->data not at mac header
(offset %d)\n",
+ offset)) {
+ return -EINVAL;
+ }
+
err = skb_ensure_writable(skb, VLAN_ETH_HLEN);
if (unlikely(err))
- goto pull;
+ return err;
skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
@@ -4501,12 +4506,13 @@ static int __skb_vlan_pop(struct sk_buff *skb, u16
*vlan_tci)
skb_set_network_header(skb, ETH_HLEN);
skb_reset_mac_len(skb);
-pull:
- __skb_pull(skb, offset);
return err;
}
+/* Pop a vlan tag either from hwaccel or from payload.
+ * Expects skb->data at mac header.
+ */
int skb_vlan_pop(struct sk_buff *skb)
{
u16 vlan_tci;
@@ -4541,29 +4547,30 @@ int skb_vlan_pop(struct sk_buff *skb)
}
EXPORT_SYMBOL(skb_vlan_pop);
+/* Push a vlan tag either into hwaccel or into payload (if hwaccel tag
present).
+ * Expects skb->data at mac header.
+ */
int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
{
if (skb_vlan_tag_present(skb)) {
- unsigned int offset = skb->data - skb_mac_header(skb);
+ int offset = skb->data - skb_mac_header(skb);
int err;
- /* __vlan_insert_tag expect skb->data pointing to mac header.
- * So change skb->data before calling it and change back to
- * original position later
- */
- __skb_push(skb, offset);
+ if (WARN_ONCE(offset,
+ "skb_vlan_push got skb with skb->data not at mac
header (offset %d)\n",
+ offset)) {
+ return -EINVAL;
+ }
+
err = __vlan_insert_tag(skb, skb->vlan_proto,
skb_vlan_tag_get(skb));
- if (err) {
- __skb_pull(skb, offset);
+ if (err)
return err;
- }
skb->protocol = skb->vlan_proto;
skb->mac_len += VLAN_HLEN;
skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
- __skb_pull(skb, offset);
}
__vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
return 0;
--
2.7.4
