From e9697e2effad50c0081b3c72002d3975f8ab4347 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 3 Aug 2018 12:38:39 +0200 Subject: 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 Signed-off-by: David S. Miller --- include/uapi/linux/l2tp.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'include') diff --git a/include/uapi/linux/l2tp.h b/include/uapi/linux/l2tp.h index 8bb8c7cfabe5..61158f5a1a5b 100644 --- a/include/uapi/linux/l2tp.h +++ b/include/uapi/linux/l2tp.h @@ -119,7 +119,7 @@ enum { L2TP_ATTR_IP_DADDR, /* u32 */ L2TP_ATTR_UDP_SPORT, /* u16 */ L2TP_ATTR_UDP_DPORT, /* u16 */ - L2TP_ATTR_MTU, /* u16 */ + L2TP_ATTR_MTU, /* u16 (not used) */ L2TP_ATTR_MRU, /* u16 (not used) */ L2TP_ATTR_STATS, /* nested */ L2TP_ATTR_IP6_SADDR, /* struct in6_addr */ -- cgit v1.2.3