linux/net/l2tp
Alice Mikityanska 5329647dad net: Use helpers to get/set UDP len tree-wide
Since BIG TCP for UDP tunnels will start using len=0 in the UDP header
as an indicator of a GSO packet bigger than 65535 bytes, this commit
introduces the following getter and setters to use tree-wide, in order
to explicitly mark places where len=0 may be expected, and handle them
properly:

1. udp_set_len() sets uh->len to its real value if it's not bigger than
65535, and to 0 otherwise: to be used in GSO context with aggregated
packets.

2. udp_set_len_short() is to be used when the length is known to fit 16
bits. It WARNs when the caller tries to assign a bigger value if
CONFIG_DEBUG_NET=y.

3. udp_get_len_short() returns len in host byte order: to be used on the
RX side to deal with non-aggregated packets, or to access the raw value
of the len field.

4. udp_get_len() decodes uh->len set by udp_set_len(). It checks whether
the packet is GSO to guard from malformed packets.

At the moment udp_set_len() is not used, a following commit will start
using it after enabling len>65535 for GSO.

Raw uh->len (in network byte order) is still accessed in a few places
for checksum calculation purposes, and to decode len=0 in udpv6_rcv for
jumbograms. udp_rcv and udpv6_rcv will be addressed by the commit that
starts using udp_set_len() to set UDP len=0 for BIG TCP packets in UDP
tunnels.

Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason A. Donenfeld <Jason@zx2c4.com>
Link: https://patch.msgid.link/20260710134242.216538-2-alice.kernel@fastmail.im
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2026-07-22 13:47:02 +02:00
..
Kconfig ipv6: convert CONFIG_IPV6 to built-in only and clean up Kconfigs 2026-03-29 11:21:22 -07:00
l2tp_core.c net: Use helpers to get/set UDP len tree-wide 2026-07-22 13:47:02 +02:00
l2tp_core.h l2tp: improve tunnel/session refcount helpers 2024-08-11 04:38:50 +01:00
l2tp_debugfs.c Convert 'alloc_obj' family to use the new default GFP_KERNEL argument 2026-02-21 17:09:51 -08:00
l2tp_eth.c net: l2tp_eth: Replace deprecated strcpy with strscpy in l2tp_eth_create 2026-02-24 13:38:33 +01:00
l2tp_ip.c net: remove addr_len argument of recvmsg() handlers 2026-03-02 18:17:17 -08:00
l2tp_ip6.c net: remove addr_len argument of recvmsg() handlers 2026-03-02 18:17:17 -08:00
l2tp_netlink.c genetlink: hold RCU in genlmsg_mcast() 2024-10-15 17:52:58 -07:00
l2tp_ppp.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2026-06-04 15:29:04 -07:00
Makefile l2tp: add tracepoint infrastructure to core 2020-08-22 12:44:37 -07:00
trace.h l2tp: add tracepoint definitions in trace.h 2020-08-22 12:44:37 -07:00