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| author | Jiri Benc <jbenc@redhat.com> | 2023-07-20 11:05:56 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2023-07-24 09:37:32 +0100 |
| commit | 94d166c5318c6edd1e079df8552233443e909c33 (patch) | |
| tree | 89965293e07cce3800f6c6fc0a455265fc8b75b0 /include/net/vxlan.h | |
| parent | a071c6ace314d7bcc8400275ea79f13b5bcc89e9 (diff) | |
vxlan: calculate correct header length for GPE
VXLAN-GPE does not add an extra inner Ethernet header. Take that into
account when calculating header length.
This causes problems in skb_tunnel_check_pmtu, where incorrect PMTU is
cached.
In the collect_md mode (which is the only mode that VXLAN-GPE
supports), there's no magic auto-setting of the tunnel interface MTU.
It can't be, since the destination and thus the underlying interface
may be different for each packet.
So, the administrator is responsible for setting the correct tunnel
interface MTU. Apparently, the administrators are capable enough to
calculate that the maximum MTU for VXLAN-GPE is (their_lower_MTU - 36).
They set the tunnel interface MTU to 1464. If you run a TCP stream over
such interface, it's then segmented according to the MTU 1464, i.e.
producing 1514 bytes frames. Which is okay, this still fits the lower
MTU.
However, skb_tunnel_check_pmtu (called from vxlan_xmit_one) uses 50 as
the header size and thus incorrectly calculates the frame size to be
1528. This leads to ICMP too big message being generated (locally),
PMTU of 1450 to be cached and the TCP stream to be resegmented.
The fix is to use the correct actual header size, especially for
skb_tunnel_check_pmtu calculation.
Fixes: e1e5314de08ba ("vxlan: implement GPE")
Signed-off-by: Jiri Benc <jbenc@redhat.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/vxlan.h')
| -rw-r--r-- | include/net/vxlan.h | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/include/net/vxlan.h b/include/net/vxlan.h index 0be91ca78d3a..1648240c9668 100644 --- a/include/net/vxlan.h +++ b/include/net/vxlan.h @@ -386,10 +386,15 @@ static inline netdev_features_t vxlan_features_check(struct sk_buff *skb, return features; } -/* IP header + UDP + VXLAN + Ethernet header */ -#define VXLAN_HEADROOM (20 + 8 + 8 + 14) -/* IPv6 header + UDP + VXLAN + Ethernet header */ -#define VXLAN6_HEADROOM (40 + 8 + 8 + 14) +static inline int vxlan_headroom(u32 flags) +{ + /* VXLAN: IP4/6 header + UDP + VXLAN + Ethernet header */ + /* VXLAN-GPE: IP4/6 header + UDP + VXLAN */ + return (flags & VXLAN_F_IPV6 ? sizeof(struct ipv6hdr) : + sizeof(struct iphdr)) + + sizeof(struct udphdr) + sizeof(struct vxlanhdr) + + (flags & VXLAN_F_GPE ? 0 : ETH_HLEN); +} static inline struct vxlanhdr *vxlan_hdr(struct sk_buff *skb) { |