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sched: consistently handle layer3 header accesses in the presence of VLANs

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There are a couple of places in net/sched/ that check skb->protocol and act
on the value there. However, in the presence of VLAN tags, the value stored
in skb->protocol can be inconsistent based on whether VLAN acceleration is
enabled. The commit quoted in the Fixes tag below fixed the users of
skb->protocol to use a helper that will always see the VLAN ethertype.

However, most of the callers don't actually handle the VLAN ethertype, but
expect to find the IP header type in the protocol field. This means that
things like changing the ECN field, or parsing diffserv values, stops
working if there's a VLAN tag, or if there are multiple nested VLAN
tags (QinQ).

To fix this, change the helper to take an argument that indicates whether
the caller wants to skip the VLAN tags or not. When skipping VLAN tags, we
make sure to skip all of them, so behaviour is consistent even in QinQ
mode.

To make the helper usable from the ECN code, move it to if_vlan.h instead
of pkt_sched.h.

v3:
- Remove empty lines
- Move vlan variable definitions inside loop in skb_protocol()
- Also use skb_protocol() helper in IP{,6}_ECN_decapsulate() and
  bpf_skb_ecn_set_ce()

v2:
- Use eth_type_vlan() helper in skb_protocol()
- Also fix code that reads skb->protocol directly
- Change a couple of 'if/else if' statements to switch constructs to avoid
  calling the helper twice

Reported-by: Ilya Ponetayev <i.ponetaev@ndmsystems.com>
Fixes: d8b9605d26 ("net: sched: fix skb->protocol use in case of accelerated vlan path")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Toke Høiland-Jørgensen
2020-07-03 22:26:43 +02:00
committed by David S. Miller
parent ad4e2b6483
commit d7bf2ebebc
19 changed files with 86 additions and 51 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
net/sched/cls_flow.c
View File

@@ -80,7 +80,7 @@ static u32 flow_get_dst(const struct sk_buff *skb, const struct flow_keys *flow)
if (dst)
return ntohl(dst);
return addr_fold(skb_dst(skb)) ^ (__force u16) tc_skb_protocol(skb);
return addr_fold(skb_dst(skb)) ^ (__force u16)skb_protocol(skb, true);
}
static u32 flow_get_proto(const struct sk_buff *skb,
@@ -104,7 +104,7 @@ static u32 flow_get_proto_dst(const struct sk_buff *skb,
if (flow->ports.ports)
return ntohs(flow->ports.dst);
return addr_fold(skb_dst(skb)) ^ (__force u16) tc_skb_protocol(skb);
return addr_fold(skb_dst(skb)) ^ (__force u16)skb_protocol(skb, true);
}
static u32 flow_get_iif(const struct sk_buff *skb)
@@ -151,7 +151,7 @@ static u32 flow_get_nfct(const struct sk_buff *skb)
static u32 flow_get_nfct_src(const struct sk_buff *skb,
const struct flow_keys *flow)
{
switch (tc_skb_protocol(skb)) {
switch (skb_protocol(skb, true)) {
case htons(ETH_P_IP):
return ntohl(CTTUPLE(skb, src.u3.ip));
case htons(ETH_P_IPV6):
@@ -164,7 +164,7 @@ fallback:
static u32 flow_get_nfct_dst(const struct sk_buff *skb,
const struct flow_keys *flow)
{
switch (tc_skb_protocol(skb)) {
switch (skb_protocol(skb, true)) {
case htons(ETH_P_IP):
return ntohl(CTTUPLE(skb, dst.u3.ip));
case htons(ETH_P_IPV6):