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Ido Schimmel 4a8c416602 ipv4: icmp: Fix source IP derivation in presence of VRFs
When the "icmp_errors_use_inbound_ifaddr" sysctl is enabled, the source
IP of ICMP error messages should be the "primary address of the
interface that received the packet that caused the icmp error".

The IPv4 ICMP code determines this interface using inet_iif() which in
the input path translates to skb->skb_iif. If the interface that
received the packet is a VRF port, skb->skb_iif will contain the ifindex
of the VRF device and not that of the receiving interface. This is
because in the input path the VRF driver overrides skb->skb_iif with the
ifindex of the VRF device itself (see vrf_ip_rcv()).

As such, the source IP that will be chosen for the ICMP error message is
either an address assigned to the VRF device itself (if present) or an
address assigned to some VRF port, not necessarily the input or output
interface.

This behavior is especially problematic when the error messages are
"Time Exceeded" messages as it means that utilities like traceroute will
show an incorrect packet path.

Solve this by determining the input interface based on the iif field in
the control block, if present. This field is set in the input path to
skb->skb_iif and is not later overridden by the VRF driver, unlike
skb->skb_iif.

This behavior is consistent with the IPv6 counterpart that already uses
the iif from the control block.

Reported-by: Andy Roulin <aroulin@nvidia.com>
Reported-by: Rajkumar Srinivasan <rajsrinivasa@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20250908073238.119240-4-idosch@nvidia.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2025-09-11 12:22:38 +02:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-09-04 13:33:00 -07:00
block block: validate QoS before calling __rq_qos_done_bio() 2025-08-26 10:34:08 -06:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
Documentation doc: mptcp: fix Netlink specs link 2025-09-10 18:28:41 -07:00
drivers net: xdp: pass full flags to xdp_update_skb_shared_info() 2025-09-11 12:00:20 +02:00
fs a ksmbd server fix 2025-09-03 20:44:15 -07:00
include ipv4: icmp: Pass IPv4 control block structure as an argument to __icmp_send() 2025-09-11 12:22:38 +02:00
init hardening: Require clang 20.1.0 for __counted_by 2025-08-29 12:04:53 -07:00
io_uring Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-09-04 13:33:00 -07:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-09-04 13:33:00 -07:00
lib hardening fixes for v6.17-rc4 2025-08-31 08:56:45 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
mm Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-09-04 13:33:00 -07:00
net ipv4: icmp: Fix source IP derivation in presence of VRFs 2025-09-11 12:22:38 +02:00
rust Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-09-04 13:33:00 -07:00
samples Significant patch series in this pull request: 2025-08-03 16:23:09 -07:00
scripts Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2025-09-04 13:33:00 -07:00
security + Features 2025-08-04 08:17:28 -07:00
sound ALSA: hda/hdmi: Add pin fix for another HP EliteDesk 800 G4 model 2025-09-01 13:51:57 +02:00
tools selftests: net: Add tests to verify team driver option set and get. 2025-09-11 11:07:55 +02:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap MAINTAINERS: Update Nobuhiro Iwamatsu's email address 2025-09-01 10:36:10 +02:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml
COPYING
CREDITS MAINTAINERS: retire Boris from TLS maintainers 2025-08-26 17:36:01 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS ptp: qoriq: convert to use generic interfaces to set loopback mode 2025-09-09 19:28:52 -07:00
Makefile Linux 6.17-rc4 2025-08-31 15:33:07 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

Linux kernel

There are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. Please read Documentation/admin-guide/README.rst first.

In order to build the documentation, use make htmldocs or make pdfdocs. The formatted documentation can also be read online at:

https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory, several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.