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| author | Guillaume Nault <g.nault@alphalink.fr> | 2018-08-03 12:38:39 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-08-03 10:03:57 -0700 |
| commit | e9697e2effad50c0081b3c72002d3975f8ab4347 (patch) | |
| tree | ffa8f583cf4fedb528944b3b1121a1471bd7f6eb /net/l2tp/l2tp_eth.c | |
| parent | 789141b215fc509defdd0f0978e4bf1bb5b31fc2 (diff) | |
| download | linux-e9697e2effad50c0081b3c72002d3975f8ab4347.tar.gz linux-e9697e2effad50c0081b3c72002d3975f8ab4347.tar.bz2 linux-e9697e2effad50c0081b3c72002d3975f8ab4347.zip | |
l2tp: ignore L2TP_ATTR_MTU
This attribute's handling is broken. It can only be used when creating
Ethernet pseudo-wires, in which case its value can be used as the
initial MTU for the l2tpeth device.
However, when handling update requests, L2TP_ATTR_MTU only modifies
session->mtu. This value is never propagated to the l2tpeth device.
Dump requests also return the value of session->mtu, which is not
synchronised anymore with the device MTU.
The same problem occurs if the device MTU is properly updated using the
generic IFLA_MTU attribute. In this case, session->mtu is not updated,
and L2TP_ATTR_MTU will report an invalid value again when dumping the
session.
It does not seem worthwhile to complexify l2tp_eth.c to synchronise
session->mtu with the device MTU. Even the ip-l2tp manpage advises to
use 'ip link' to initialise the MTU of l2tpeth devices (iproute2 does
not handle L2TP_ATTR_MTU at all anyway). So let's just ignore it
entirely.
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/l2tp/l2tp_eth.c')
| -rw-r--r-- | net/l2tp/l2tp_eth.c | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/net/l2tp/l2tp_eth.c b/net/l2tp/l2tp_eth.c index cfca5e63ae31..3728986ec885 100644 --- a/net/l2tp/l2tp_eth.c +++ b/net/l2tp/l2tp_eth.c @@ -234,14 +234,11 @@ static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel, overhead += sizeof(struct udphdr); dev->needed_headroom += sizeof(struct udphdr); } - if (session->mtu != 0) { - dev->mtu = session->mtu; - dev->needed_headroom += session->hdr_len; - return; - } + lock_sock(tunnel->sock); l3_overhead = kernel_sock_ip_overhead(tunnel->sock); release_sock(tunnel->sock); + if (l3_overhead == 0) { /* L3 Overhead couldn't be identified, this could be * because tunnel->sock was NULL or the socket's @@ -255,12 +252,12 @@ static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel, */ overhead += session->hdr_len + ETH_HLEN + l3_overhead; - /* If PMTU discovery was enabled, use discovered MTU on L2TP device */ - mtu = l2tp_tunnel_dst_mtu(tunnel); - if (mtu) + mtu = l2tp_tunnel_dst_mtu(tunnel) - overhead; + if (mtu < dev->min_mtu || mtu > dev->max_mtu) + dev->mtu = ETH_DATA_LEN - overhead; + else dev->mtu = mtu; - session->mtu = dev->mtu - overhead; - dev->mtu = session->mtu; + dev->needed_headroom += session->hdr_len; } |