Kernel: T8605: net/l2tp: allow unmanaged tunnel setup without route to peer

Kernel-created L2TPv3 tunnels (genetlink L2TP_CMD_TUNNEL_CREATE without
L2TP_ATTR_FD) used udp_sock_create() and kernel_connect(), which invoke
__ip4_datagram_connect() / __ip6_datagram_connect(). Those paths insist on
a successful FIB lookup at connect time. If no route to the configured
remote existed yet, tunnel and interface creation failed.

The data path already resolves routes on transmit (e.g. __ip_queue_xmit(),
inet6_csk_route_socket()). This change defers requiring a route until
packets are sent.

Details:
- UDP encapsulation: bind with udp_sock_create() after zeroing peer_udp_port,
  then l2tp_udp_sk_set_peer() sets daddr/dport and socket "connected" state
  without caching sk_dst from connect.
- IPv4 L2TP/IP (l2tp_ip): on -ENETUNREACH / -EHOSTUNREACH from
  __ip4_datagram_connect(), l2tp_ip_connect_deferred() installs peer and
  bind-table updates without a connect-time route.
- IPv6 L2TP/IP (l2tp_ip6): same for __ip6_datagram_connect(), including
  IPv4-mapped peers and scope / bound-device checks aligned with the normal
  connect path.

Forwarding still only happens once the FIB can reach the peer. Until then
outgoing packets follow the existing no-route drop path.

Assisted-by: Cursor:claude-4.6-opus
Signed-off-by: Christian Breunig <christian@breunig.cc>

0 files changed, 0 insertions, 0 deletions