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77a2d673d5
linux/net/ipv4
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Stefano Brivio 77a2d673d5 tunnels: Fix off-by-one in lower MTU bounds for ICMP/ICMPv6 replies 
Jianlin reports that a bridged IPv6 VXLAN endpoint, carrying IPv6
packets over a link with a PMTU estimation of exactly 1350 bytes,
won't trigger ICMPv6 Packet Too Big replies when the encapsulated
datagrams exceed said PMTU value. VXLAN over IPv6 adds 70 bytes of
overhead, so an ICMPv6 reply indicating 1280 bytes as inner MTU
would be legitimate and expected.

This comes from an off-by-one error I introduced in checks added
as part of commit 4cb47a8644 ("tunnels: PMTU discovery support
for directly bridged IP packets"), whose purpose was to prevent
sending ICMPv6 Packet Too Big messages with an MTU lower than the
smallest permissible IPv6 link MTU, i.e. 1280 bytes.

In iptunnel_pmtud_check_icmpv6(), avoid triggering a reply only if
the advertised MTU would be less than, and not equal to, 1280 bytes.

Also fix the analogous comparison for IPv4, that is, skip the ICMP
reply only if the resulting MTU is strictly less than 576 bytes.

This becomes apparent while running the net/pmtu.sh bridged VXLAN
or GENEVE selftests with adjusted lower-link MTU values. Using
e.g. GENEVE, setting ll_mtu to the values reported below, in the
test_pmtu_ipvX_over_bridged_vxlanY_or_geneveY_exception() test
function, we can see failures on the following tests:

             test                | ll_mtu
  -------------------------------|--------
  pmtu_ipv4_br_geneve4_exception |   626
  pmtu_ipv6_br_geneve4_exception |  1330
  pmtu_ipv6_br_geneve6_exception |  1350

owing to the different tunneling overheads implied by the
corresponding configurations.

Reported-by: Jianlin Shi <jishi@redhat.com>
Fixes: 4cb47a8644 ("tunnels: PMTU discovery support for directly bridged IP packets")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Link: https://lore.kernel.org/r/4f5fc2f33bfdf8409549fafd4f952b008bf04d63.1604681709.git.sbrivio@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2020-11-09 15:39:39 -08:00
..
bpfilter net: Revert "net: optimize the sockptr_t for unified kernel/user address spaces" 2020-08-10 12:06:44 -07:00
netfilter netfilter: use actual socket sk rather than skb sk when routing harder 2020-10-30 12:57:39 +01:00
af_inet.c io_uring: allow tcp ancillary data for __sys_recvmsg_sock() 2020-08-24 16:16:06 -07:00
ah4.c inet: Use fallthrough; 2020-03-12 15:55:00 -07:00
arp.c inet: Use fallthrough; 2020-03-12 15:55:00 -07:00
bpf_tcp_ca.c bpf: Change bpf_sk_storage_*() to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON 2020-09-25 13:58:01 -07:00
cipso_ipv4.c cipso: fix 'audit_secid' kernel-doc warning in cipso_ipv4.c 2020-09-08 20:03:36 -07:00
datagram.c inet: stop leaking jiffies on the wire 2019-11-01 14:57:52 -07:00
devinet.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-05-31 17:48:46 -07:00
esp4_offload.c net: Add MODULE_DESCRIPTION entries to network modules 2020-06-20 21:33:57 -07:00
esp4.c ESP: Export esp_output_fill_trailer function 2020-02-19 13:52:32 +01:00
fib_frontend.c ipv4: Initialize flowi4_multipath_hash in data path 2020-09-14 14:54:56 -07:00
fib_lookup.h net: add net available in build_state 2020-03-29 22:30:57 -07:00
fib_notifier.c net: fib_notifier: propagate extack down to the notifier block callback 2019-10-04 11:10:56 -07:00
fib_rules.c fib: use indirect call wrappers in the most common fib_rules_ops 2020-07-28 17:42:31 -07:00
fib_semantics.c net: Fix the arp error in some cases 2020-06-18 20:21:51 -07:00
fib_trie.c ipv4: Silence suspicious RCU usage warning 2020-08-26 15:58:48 -07:00
fou.c genetlink: move to smaller ops wherever possible 2020-10-02 19:11:11 -07:00
gre_demux.c gre: fix uninit-value in __iptunnel_pull_header 2020-03-08 21:25:37 -07:00
gre_offload.c net: gre: recompute gre csum for sctp over gre tunnels 2020-08-03 15:29:44 -07:00
icmp.c icmp: randomize the global rate limiter 2020-10-16 16:47:09 -07:00
igmp.c ip*_mc_gsfget(): lift copyout of struct group_filter into callers 2020-05-20 20:31:27 -04:00
inet_connection_sock.c inet: remove icsk_ack.blocked 2020-09-30 14:21:30 -07:00
inet_diag.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-22 16:45:34 -07:00
inet_fragment.c inet: frags: re-introduce skb coalescing for local delivery 2019-08-08 15:55:10 -07:00
inet_hashtables.c net: ipv4: remove unused arg exact_dif in compute_score 2020-08-31 13:08:29 -07:00
inet_timewait_sock.c
inetpeer.c inetpeer: fix data-race in inet_putpeer / inet_putpeer 2019-11-07 16:15:56 -08:00
ip_forward.c ipv4: Revert removal of rt_uses_gateway 2019-09-20 18:23:33 -07:00
ip_fragment.c inet: frags: re-introduce skb coalescing for local delivery 2019-08-08 15:55:10 -07:00
ip_gre.c ip_gre: set dev->hard_header_len and dev->needed_headroom properly 2020-10-13 18:35:29 -07:00
ip_input.c bpf: Add socket assign support 2020-03-30 13:45:04 -07:00
ip_options.c net: clean up codestyle for net/ipv4 2020-08-25 06:28:02 -07:00
ip_output.c networking changes for the 5.10 merge window 2020-10-15 18:42:13 -07:00
ip_sockglue.c net: Remove duplicated midx check against 0 2020-08-25 06:23:59 -07:00
ip_tunnel_core.c tunnels: Fix off-by-one in lower MTU bounds for ICMP/ICMPv6 replies 2020-11-09 15:39:39 -08:00
ip_tunnel.c ip_tunnel: fix over-mtu packet send fail without TUNNEL_DONT_FRAGMENT flags 2020-10-31 17:19:02 -07:00
ip_vti.c ipv4: use dev_sw_netstats_rx_add() 2020-10-06 06:23:21 -07:00
ipcomp.c ipcomp: assign if_id to child tunnel from parent tunnel 2020-07-09 12:55:37 +02:00
ipconfig.c Documentation: nfsroot.rst: Fix references to nfsroot.rst 2020-03-02 13:11:46 -07:00
ipip.c net: ipip: implement header_ops->parse_protocol for AF_PACKET 2020-06-30 12:29:39 -07:00
ipmr_base.c net: fib_notifier: propagate extack down to the notifier block callback 2019-10-04 11:10:56 -07:00
ipmr.c ipmr: Use full VIF ID in netlink cache reports 2020-09-10 12:25:51 -07:00
Kconfig net: ipv4: remove duplicate "the the" phrase in Kconfig text 2020-08-18 16:02:16 -07:00
Makefile udp_tunnel: add central NIC RX port offload infrastructure 2020-07-10 13:54:00 -07:00
metrics.c
netfilter.c netfilter: use actual socket sk rather than skb sk when routing harder 2020-10-30 12:57:39 +01:00
netlink.c
nexthop.c nexthop: Fix performance regression in nexthop deletion 2020-10-19 20:07:15 -07:00
ping.c net: clean up codestyle 2020-08-31 12:33:34 -07:00
proc.c tcp: skip DSACKs with dubious sequence ranges 2020-09-24 20:15:45 -07:00
protocol.c
raw_diag.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-03-12 22:34:48 -07:00
raw.c networking changes for the 5.10 merge window 2020-10-15 18:42:13 -07:00
route.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-10-15 12:43:21 -07:00
syncookies.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-10-05 18:40:01 -07:00
sysctl_net_ipv4.c tcp: reflect tos value received in SYN to the socket 2020-09-10 13:15:40 -07:00
tcp_bbr.c tcp_bbr: improve arithmetic division in bbr_update_bw() 2020-01-21 10:45:49 +01:00
tcp_bic.c tcp: fix stretch ACK bugs in BIC 2020-03-16 18:26:54 -07:00
tcp_bpf.c net: sk_msg: Simplify sk_psock initialization 2020-08-21 15:16:11 -07:00
tcp_cdg.c
tcp_cong.c tcp: Simplify tcp_set_congestion_control() load=false case 2020-09-10 20:53:01 -07:00
tcp_cubic.c tcp_cubic: fix spurious HYSTART_DELAY exit upon drop in min RTT 2020-06-25 16:08:47 -07:00
tcp_dctcp.c
tcp_dctcp.h
tcp_diag.c inet_diag: Move the INET_DIAG_REQ_BYTECODE nlattr to cb->data 2020-02-27 18:50:19 -08:00
tcp_fastopen.c bpf: tcp: Add bpf_skops_established() 2020-08-24 14:35:00 -07:00
tcp_highspeed.c Replace HTTP links with HTTPS ones: IPv* 2020-07-06 13:23:03 -07:00
tcp_htcp.c Replace HTTP links with HTTPS ones: IPv* 2020-07-06 13:23:03 -07:00
tcp_hybla.c
tcp_illinois.c
tcp_input.c tcp: Prevent low rmem stalls with SO_RCVLOWAT. 2020-10-23 19:11:20 -07:00
tcp_ipv4.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-10-08 15:44:50 -07:00
tcp_lp.c
tcp_metrics.c genetlink: move to smaller ops wherever possible 2020-10-02 19:11:11 -07:00
tcp_minisocks.c bpf: tcp: Do not limit cb_flags when creating child sk from listen sk 2020-10-02 11:34:48 -07:00
tcp_nv.c
tcp_offload.c
tcp_output.c tcp: add exponential backoff in __tcp_send_ack() 2020-09-30 14:21:30 -07:00
tcp_rate.c
tcp_recovery.c tcp: move tcp_mark_skb_lost 2020-09-25 17:17:14 -07:00
tcp_scalable.c net: ipv4: delete repeated words 2020-08-24 17:31:20 -07:00
tcp_timer.c inet: remove icsk_ack.blocked 2020-09-30 14:21:30 -07:00
tcp_ulp.c bpf: sockmap: Only check ULP for TCP sockets 2020-03-09 22:34:58 +01:00
tcp_vegas.c tcp: use semicolons rather than commas to separate statements 2020-10-13 17:11:52 -07:00
tcp_vegas.h
tcp_veno.c Replace HTTP links with HTTPS ones: IPv* 2020-07-06 13:23:03 -07:00
tcp_westwood.c
tcp_yeah.c tcp: fix stretch ACK bugs in Yeah 2020-03-16 18:26:55 -07:00
tcp.c tcp: Prevent low rmem stalls with SO_RCVLOWAT. 2020-10-23 19:11:20 -07:00
tunnel4.c tunnel4: add cb_handler to struct xfrm_tunnel 2020-07-09 12:51:36 +02:00
udp_bpf.c net: sk_msg: Simplify sk_psock initialization 2020-08-21 15:16:11 -07:00
udp_diag.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-03-12 22:34:48 -07:00
udp_impl.h net: pass a sockptr_t into ->setsockopt 2020-07-24 15:41:54 -07:00
udp_offload.c udp: initialize is_flist with 0 in udp_gro_receive 2020-03-30 10:35:03 -07:00
udp_tunnel_core.c udp_tunnel: add central NIC RX port offload infrastructure 2020-07-10 13:54:00 -07:00
udp_tunnel_nic.c udp_tunnel: add the ability to share port tables 2020-09-28 12:50:12 -07:00
udp_tunnel_stub.c udp_tunnel: add central NIC RX port offload infrastructure 2020-07-10 13:54:00 -07:00
udp.c net: ipv4: delete repeated words 2020-08-24 17:31:20 -07:00
udplite.c net/ipv4: remove compat_ip_{get,set}sockopt 2020-07-19 18:16:41 -07:00
xfrm4_input.c xfrm: state: remove extract_input indirection from xfrm_state_afinfo 2020-05-06 09:40:08 +02:00
xfrm4_output.c xfrm: fix unused variable warning if CONFIG_NETFILTER=n 2020-05-11 15:12:27 +02:00
xfrm4_policy.c net: add bool confirm_neigh parameter for dst_ops.update_pmtu 2019-12-24 22:28:54 -08:00
xfrm4_protocol.c xfrm: add route lookup to xfrm4_rcv_encap 2019-12-09 09:59:07 +01:00
xfrm4_state.c xfrm: remove output_finish indirection from xfrm_state_afinfo 2020-05-06 09:40:08 +02:00
xfrm4_tunnel.c xfrm: interface: fix the priorities for ipip and ipv6 tunnels 2020-10-09 12:29:48 +02:00