linux/include/net
Maciej Żenczykowski 02a1b175b0 net/ipv4: always honour route mtu during forwarding
Documentation/networking/ip-sysctl.txt:46 says:
  ip_forward_use_pmtu - BOOLEAN
    By default we don't trust protocol path MTUs while forwarding
    because they could be easily forged and can lead to unwanted
    fragmentation by the router.
    You only need to enable this if you have user-space software
    which tries to discover path mtus by itself and depends on the
    kernel honoring this information. This is normally not the case.
    Default: 0 (disabled)
    Possible values:
    0 - disabled
    1 - enabled

Which makes it pretty clear that setting it to 1 is a potential
security/safety/DoS issue, and yet it is entirely reasonable to want
forwarded traffic to honour explicitly administrator configured
route mtus (instead of defaulting to device mtu).

Indeed, I can't think of a single reason why you wouldn't want to.
Since you configured a route mtu you probably know better...

It is pretty common to have a higher device mtu to allow receiving
large (jumbo) frames, while having some routes via that interface
(potentially including the default route to the internet) specify
a lower mtu.

Note that ipv6 forwarding uses device mtu unless the route is locked
(in which case it will use the route mtu).

This approach is not usable for IPv4 where an 'mtu lock' on a route
also has the side effect of disabling TCP path mtu discovery via
disabling the IPv4 DF (don't frag) bit on all outgoing frames.

I'm not aware of a way to lock a route from an IPv6 RA, so that also
potentially seems wrong.

Signed-off-by: Maciej Żenczykowski <maze@google.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Lorenzo Colitti <lorenzo@google.com>
Cc: Sunmeet Gill (Sunny) <sgill@quicinc.com>
Cc: Vinay Paradkar <vparadka@qti.qualcomm.com>
Cc: Tyler Wear <twear@quicinc.com>
Cc: David Ahern <dsahern@kernel.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-09-24 19:51:16 -07:00
..
9p net: 9p: drop duplicate word in comment 2020-07-15 20:34:11 -07:00
bluetooth Bluetooth: Enable controller RPA resolution using Experimental feature 2020-07-30 11:14:05 +02:00
caif net: caif: drop duplicate words in comments 2020-07-15 20:34:11 -07:00
iucv net/af_iucv: clean up function prototypes 2020-05-19 12:50:14 -07:00
netfilter netfilter: nf_tables: fix destination register zeroing 2020-08-21 19:00:33 +02:00
netns netfilter: nf_tables: coalesce multiple notifications into one skbuff 2020-09-08 13:02:44 +02:00
nfc NFC: Replace zero-length array with flexible-array member 2020-02-27 12:06:20 -08:00
phonet treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 336 2019-06-05 17:37:07 +02:00
sctp net: sctp: Fix IPv6 ancestor_size calc in sctp_copy_descendant 2020-09-20 14:15:12 -07:00
tc_act net:qos: police action offloading parameter 'burst' change to the original value 2020-06-29 17:33:42 -07:00
6lowpan.h 6lowpan: Replace zero-length array with flexible-array member 2020-02-28 14:51:30 +01:00
act_api.h net_sched: defer tcf_idr_insert() in tcf_action_init_1() 2020-09-24 19:46:21 -07:00
addrconf.h ipv6: some fixes for ipv6_dev_find() 2020-08-18 15:58:53 -07:00
af_ieee802154.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
af_rxrpc.h rxrpc: Make rxrpc_kernel_get_srtt() indicate validity 2020-08-20 18:21:28 +01:00
af_unix.h unix: uses an atomic type for scm files accounting 2020-02-28 12:12:53 -08:00
af_vsock.h vsock: add local transport support in the vsock core 2019-12-11 15:01:23 -08:00
ah.h
arp.h net: avoid potential false sharing in neighbor related code 2019-11-06 16:14:48 -08:00
atmclip.h
ax25.h ax25: fix possible use-after-free 2019-01-23 11:18:00 -08:00
ax88796.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
bareudp.h bareudp: Reverted support to enable & disable rx metadata collection 2020-07-21 18:30:47 -07:00
bond_3ad.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 90 2019-05-24 17:37:53 +02:00
bond_alb.h bonding/alb: Add helper functions to get the xmit slave 2020-05-01 12:15:37 -07:00
bond_options.h bonding: add an option to specify a delay between peer notifications 2019-07-04 12:30:48 -07:00
bonding.h bonding: allow xfrm offload setup post-module-load 2020-07-01 15:53:32 -07:00
bpf_sk_storage.h bpf: INET_DIAG support in bpf_sk_storage 2020-02-27 18:50:19 -08:00
busy_poll.h net: Avoid overwriting valid skb->napi_id 2020-06-20 17:30:59 -07:00
calipso.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13 2019-05-21 11:28:45 +02:00
cfg80211-wext.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
cfg80211.h cfg80211: invert HE BSS color 'disabled' to 'enabled' 2020-07-31 09:27:02 +02:00
cfg802154.h cfg802154: Replace zero-length array with flexible-array member 2020-02-29 14:39:08 +01:00
checksum.h default csum_and_copy_to_user(): don't bother with access_ok() 2020-05-29 16:11:50 -04:00
cipso_ipv4.h cipso: Remove unused inline functions 2020-07-15 07:45:24 -07:00
cls_cgroup.h bpf: Allow to retrieve cgroup v1 classid from v2 hooks 2020-03-27 19:40:38 -07:00
codel.h
codel_impl.h
codel_qdisc.h
compat.h net: simplify cBPF setsockopt compat handling 2020-07-19 18:16:40 -07:00
datalink.h
dcbevent.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
dcbnl.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 201 2019-05-30 11:29:52 -07:00
devlink.h devlink: Pass extack when setting trap's action and group's parameters 2020-08-03 18:06:46 -07:00
dn.h
dn_dev.h
dn_fib.h net: dn_fib: Replace zero-length array with flexible-array member 2020-02-29 21:52:20 -08:00
dn_neigh.h
dn_nsp.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 24 2019-05-21 11:52:39 +02:00
dn_route.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 24 2019-05-21 11:52:39 +02:00
drop_monitor.h Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-03-31 17:29:33 -07:00
dsa.h net: dsa: stop overriding master's ndo_get_phys_port_name 2020-07-23 15:14:58 -07:00
dsfield.h ipv6: Annotate bitwise IPv6 dsfield pointer cast 2019-12-16 16:09:44 -08:00
dst.h tunnels: PMTU discovery support for directly bridged IP packets 2020-08-04 13:01:45 -07:00
dst_cache.h
dst_metadata.h
dst_ops.h net/dst: use a smaller percpu_counter batch for dst entries accounting 2020-05-08 21:33:33 -07:00
erspan.h erspan: Add type I version 0 support. 2020-05-05 13:23:29 -07:00
esp.h ESP: Export esp_output_fill_trailer function 2020-02-19 13:52:32 +01:00
espintcp.h xfrm: espintcp: save and call old ->sk_destruct 2020-04-20 07:34:16 +02:00
ethoc.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
failover.h
fib_notifier.h ipv6: Remove old route notifications and convert listeners 2019-12-24 22:37:30 -08:00
fib_rules.h fib: use indirect call wrappers in the most common fib_rules_ops 2020-07-28 17:42:31 -07:00
firewire.h
flow.h ipv4: Initialize flowi4_multipath_hash in data path 2020-09-14 14:54:56 -07:00
flow_dissector.h net/flow_dissector: add packet hash dissection 2020-07-24 15:23:31 -07:00
flow_offload.h Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-08-05 20:13:21 -07:00
fou.h
fq.h net/fq_impl: use skb_get_hash instead of skb_get_hash_perturb 2020-07-31 09:24:24 +02:00
fq_impl.h net/fq_impl: use skb_get_hash instead of skb_get_hash_perturb 2020-07-31 09:24:24 +02:00
garp.h treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
gen_stats.h net_sched: extend packet counter to 64bit 2019-11-05 18:20:55 -08:00
genetlink.h genetlink: remove genl_bind 2020-07-01 15:49:11 -07:00
geneve.h net: Move the definition of the default Geneve udp port to public header file 2019-03-22 12:09:31 -07:00
gre.h
gro_cells.h
gtp.h
gue.h GUE: Fix a typo 2020-06-22 21:12:44 -07:00
hwbm.h net: hwbm: if CONFIG_NET_HWBM unset, make stub functions static 2019-10-25 16:24:32 -07:00
icmp.h icmp: introduce helper for nat'd source address in network device context 2020-02-13 14:19:00 -08:00
ieee80211_radiotap.h mac80211: add radiotap flag to prevent sequence number overwrite 2020-07-31 09:27:00 +02:00
ieee802154_netdev.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
if_inet6.h ipv6: Replace zero-length array with flexible-array 2020-05-11 13:18:54 -07:00
ife.h net: ife: drop include of module.h from net/ife.h 2019-04-22 21:50:53 -07:00
ila.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
inet6_connection_sock.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
inet6_hashtables.h net: Track socket refcounts in skb_steal_sock() 2020-03-30 13:45:04 -07:00
inet_common.h bpf: Allow any port in bpf_bind helper 2020-05-09 00:48:20 +02:00
inet_connection_sock.h net: refactor bind_bucket fastreuse into helper 2020-08-11 15:49:08 -07:00
inet_ecn.h sched: consistently handle layer3 header accesses in the presence of VLANs 2020-07-03 14:34:53 -07:00
inet_frag.h inet: frags: re-introduce skb coalescing for local delivery 2019-08-08 15:55:10 -07:00
inet_hashtables.h dccp: Fix possible memleak in dccp_init and dccp_fini 2020-06-09 13:26:23 -07:00
inet_sock.h icmp: support rfc 4884 2020-07-19 19:20:22 -07:00
inet_timewait_sock.h tcp: honor SO_PRIORITY in TIME_WAIT state 2019-09-27 12:05:02 +02:00
inetpeer.h net: ipv4: use a dedicated counter for icmp_v4 redirect packets 2019-02-08 21:50:15 -08:00
ip.h net/ipv4: always honour route mtu during forwarding 2020-09-24 19:51:16 -07:00
ip6_checksum.h tcp: remove indirect calls for icsk->icsk_af_ops->send_check 2020-06-20 17:47:53 -07:00
ip6_fib.h net: ip6_fib.h: drop duplicate word in comment 2020-07-15 20:34:11 -07:00
ip6_route.h ipv6: lift copy_from_user out of ipv6_route_ioctl 2020-05-18 17:35:02 -07:00
ip6_tunnel.h ip6_tunnel: allow not to count pkts on tstats by passing dev as NULL 2019-06-18 20:48:45 -04:00
ip_fib.h ipv4: nexthop version of fib_info_nh_uses_dev 2020-05-26 16:06:07 -07:00
ip_tunnels.h tunnels: PMTU discovery support for directly bridged IP packets 2020-08-04 13:01:45 -07:00
ip_vs.h ipvs: queue delayed work to expire no destination connections if expire_nodest_conn=1 2020-07-22 01:17:59 +02:00
ipcomp.h
ipconfig.h
ipv6.h net: pass a sockptr_t into ->setsockopt 2020-07-24 15:41:54 -07:00
ipv6_frag.h inet: fix various use-after-free in defrags units 2019-06-19 11:37:47 -04:00
ipv6_stubs.h Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2020-05-29 13:02:33 -07:00
ipx.h bonding/alb: properly access headers in bond_alb_xmit() 2020-02-05 14:28:09 +01:00
iw_handler.h
kcm.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
l3mdev.h l3mdev: add infrastructure for table to VRF mapping 2020-06-20 17:22:22 -07:00
lag.h
lapb.h
lib80211.h
llc.h
llc_c_ac.h
llc_c_ev.h
llc_c_st.h
llc_conn.h llc: fix sk_buff leak in llc_conn_service() 2019-10-08 13:23:05 -07:00
llc_if.h
llc_pdu.h
llc_s_ac.h
llc_s_ev.h
llc_s_st.h
llc_sap.h
lwtunnel.h net: add net available in build_state 2020-03-29 22:30:57 -07:00
mac80211.h mac80211: add a function for running rx without passing skbs to the stack 2020-07-31 09:27:01 +02:00
mac802154.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 174 2019-05-30 11:26:41 -07:00
macsec.h net: macsec: add support for getting offloaded stats 2020-03-26 20:17:36 -07:00
mip6.h net: mip6: Replace zero-length array with flexible-array member 2020-03-02 11:16:27 -08:00
mld.h net: ipv6: mld: Replace zero-length array with flexible-array member 2020-02-29 21:52:20 -08:00
mpls.h net: Make mpls_entry_encode() available for generic users 2020-05-29 21:20:20 -07:00
mpls_iptunnel.h net: mpls: Replace zero-length array with flexible-array member 2020-02-28 12:08:37 -08:00
mptcp.h mptcp: subflow: add mptcp_subflow_init_cookie_req helper 2020-07-31 16:55:32 -07:00
mrp.h treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
ncsi.h
ndisc.h ipv6: ndisc: adjust ndisc_ifinfo_sysctl_change prototype 2020-08-24 06:40:07 -07:00
neighbour.h net/sysctl: remove leftover __user annotations on neigh_proc_dointvec* 2020-06-08 10:13:56 -04:00
net_failover.h
net_namespace.h net: Introduce netns_bpf for BPF programs attached to netns 2020-06-01 15:21:02 -07:00
net_ratelimit.h
netevent.h
netlabel.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 13 2019-05-21 11:28:45 +02:00
netlink.h netlink: fix doc about nlmsg_parse/nla_validate 2020-09-10 15:13:43 -07:00
netprio_cgroup.h netprio: use css ID instead of cgroup ID 2019-11-12 08:18:03 -08:00
netrom.h net: netrom: Fix error cleanup path of nr_proto_init 2019-04-11 13:59:49 -07:00
nexthop.h vxlan: Remove access to nexthop group struct 2020-06-10 13:20:20 -07:00
nl802154.h
nsh.h
p8022.h
page_pool.h net: page_pool: API cleanup and comments 2020-02-20 10:09:25 -08:00
pie.h pie: realign comment 2020-03-04 13:25:55 -08:00
ping.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
pkt_cls.h net: sched: Do not drop root lock in tcf_qevent_handle() 2020-07-16 16:48:34 -07:00
pkt_sched.h sched: consistently handle layer3 header accesses in the presence of VLANs 2020-07-03 14:34:53 -07:00
pptp.h
protocol.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
psample.h net: sched: take reference to psample group in flow_action infra 2019-09-16 09:18:03 +02:00
psnap.h
raw.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
rawv6.h
red.h net: sched: RED: Introduce an ECN nodrop mode 2020-03-14 21:03:46 -07:00
regulatory.h net/wireless: regulatory.h: drop duplicate word in comment 2020-07-31 09:24:23 +02:00
request_sock.h tcp: rename request_sock cookie_ts bit to syncookie 2020-07-31 16:55:32 -07:00
rose.h
route.h Remove DST_HOST 2020-03-23 21:57:44 -07:00
rpl.h net: ipv6: Use struct_size() helper and kcalloc() 2020-06-23 20:27:09 -07:00
rsi_91x.h
rtnetlink.h
rtnh.h net: Rename net/nexthop.h net/rtnh.h 2019-04-22 21:47:25 -07:00
sch_generic.h net/sched: act_ct: fix miss set mru for ovs after defrag in act_ct 2020-08-03 15:04:48 -07:00
scm.h fs: Move __scm_install_fd() to __receive_fd() 2020-07-13 11:03:44 -07:00
secure_seq.h
seg6.h seg6: fix seg6_validate_srh() to avoid slab-out-of-bounds 2020-06-04 15:39:32 -07:00
seg6_hmac.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
seg6_local.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
slhc_vj.h
smc.h net/smc: introduce bookkeeping of SMCD link groups 2019-11-15 12:28:28 -08:00
snmp.h net/tls: add skeleton of MIB statistics 2019-10-05 16:29:00 -07:00
sock.h dlm for 5.9 2020-08-06 19:44:25 -07:00
sock_reuseport.h net: sock_reuseport: Replace zero-length array with flexible-array member 2020-02-29 21:52:19 -08:00
Space.h
stp.h
strparser.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
switchdev.h switchdev: mrp: Extend switchdev API for MRP Interconnect 2020-07-14 13:46:42 -07:00
tcp.h tcp: correct read of TFO keys on big endian systems 2020-08-10 12:12:35 -07:00
tcp_states.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
timewait_sock.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 152 2019-05-30 11:26:32 -07:00
tipc.h
tls.h net/tls: fix sign extension issue when left shifting u16 value 2020-06-30 13:36:56 -07:00
tls_toe.h net/tls: rename tls_hw_* functions tls_toe_* 2019-10-04 14:07:07 -07:00
transp_v6.h tcp: move ipv4_specific to tcp include file 2020-06-23 20:10:15 -07:00
tso.h net: tso: cache transport header length 2020-06-18 20:46:23 -07:00
tun_proto.h
udp.h net/udp: switch udp_lib_setsockopt to sockptr_t 2020-07-24 15:41:54 -07:00
udp_tunnel.h udp_tunnel: add the ability to hard-code IANA VXLAN 2020-08-03 10:13:54 -07:00
udplite.h
vsock_addr.h vsock: remove include/linux/vm_sockets.h file 2019-11-14 18:12:17 -08:00
vxlan.h net: sched: only keep the available bits when setting vxlan md->gbp 2020-09-14 16:49:39 -07:00
wext.h
wimax.h net: wimax: fix duplicate words in comments 2020-07-15 20:34:02 -07:00
x25.h net/x25: add new state X25_STATE_5 2019-12-09 10:28:43 -08:00
x25device.h
xdp.h bpf, xdp: Remove XDP_QUERY_PROG and XDP_QUERY_PROG_HW XDP commands 2020-07-25 20:37:02 -07:00
xdp_priv.h page_pool: do not release pool until inflight == 0. 2019-11-16 12:39:10 -08:00
xdp_sock.h xsk: Add new statistics 2020-07-13 15:32:56 -07:00
xdp_sock_drv.h xsk: Remove MEM_TYPE_ZERO_COPY and corresponding code 2020-05-21 17:31:27 -07:00
xfrm.h Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-08-02 01:02:12 -07:00
xsk_buff_pool.h xsk: Replace the cheap_dma flag with a dma_need_sync flag 2020-06-30 15:44:03 +02:00