path: root/net/l2tp/l2tp_netlink.c
diff options
authorJames Chapman <jchapman@katalix.com>2018-01-03 22:48:06 +0000
committerDavid S. Miller <davem@davemloft.net>2018-01-05 11:03:19 -0500
commit900631ee6a2651dc4fbaecb8ef9fa5f1e3378853 (patch)
treee14797b7111a65bcccf8efe27e900045afe0f28f /net/l2tp/l2tp_netlink.c
parentl2tp: revert "l2tp: fix missing print session offset info" (diff)
l2tp: remove configurable payload offset
If L2TP_ATTR_OFFSET is set to a non-zero value in L2TPv3 tunnels, it results in L2TPv3 packets being transmitted which might not be compliant with the L2TPv3 RFC. This patch has l2tp ignore the offset setting and send all packets with no offset. In more detail: L2TPv2 supports a variable offset from the L2TPv2 header to the payload. The offset value is indicated by an optional field in the L2TP header. Our L2TP implementation already detects the presence of the optional offset and skips that many bytes when handling data received packets. All transmitted packets are always transmitted with no offset. L2TPv3 has no optional offset field in the L2TPv3 packet header. Instead, L2TPv3 defines optional fields in a "Layer-2 Specific Sublayer". At the time when the original L2TP code was written, there was talk at IETF of offset being implemented in a new Layer-2 Specific Sublayer. A L2TP_ATTR_OFFSET netlink attribute was added so that this offset could be configured and the intention was to allow it to be also used to set the tx offset for L2TPv2. However, no L2TPv3 offset was ever specified and the L2TP_ATTR_OFFSET parameter was forgotten about. Setting L2TP_ATTR_OFFSET results in L2TPv3 packets being transmitted with the specified number of bytes padding between L2TPv3 header and payload. This is not compliant with L2TPv3 RFC3931. This change removes the configurable offset altogether while retaining L2TP_ATTR_OFFSET for backwards compatibility. Any L2TP_ATTR_OFFSET value is ignored. Signed-off-by: James Chapman <jchapman@katalix.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/l2tp/l2tp_netlink.c')
1 files changed, 0 insertions, 3 deletions
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index a1f24fb2be98..e1ca29f79821 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -547,9 +547,6 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
if (tunnel->version > 2) {
- if (info->attrs[L2TP_ATTR_OFFSET])
- cfg.offset = nla_get_u16(info->attrs[L2TP_ATTR_OFFSET]);
if (info->attrs[L2TP_ATTR_DATA_SEQ])
cfg.data_seq = nla_get_u8(info->attrs[L2TP_ATTR_DATA_SEQ]);