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Martynas Pumputis 68dbe92d67 bpf: Derive source IP addr via bpf_*_fib_lookup()
commit dab4e1f06c upstream.

Extend the bpf_fib_lookup() helper by making it to return the source
IPv4/IPv6 address if the BPF_FIB_LOOKUP_SRC flag is set.

For example, the following snippet can be used to derive the desired
source IP address:

    struct bpf_fib_lookup p = { .ipv4_dst = ip4->daddr };

    ret = bpf_skb_fib_lookup(skb, p, sizeof(p),
            BPF_FIB_LOOKUP_SRC | BPF_FIB_LOOKUP_SKIP_NEIGH);
    if (ret != BPF_FIB_LKUP_RET_SUCCESS)
        return TC_ACT_SHOT;

    /* the p.ipv4_src now contains the source address */

The inability to derive the proper source address may cause malfunctions
in BPF-based dataplanes for hosts containing netdevs with more than one
routable IP address or for multi-homed hosts.

For example, Cilium implements packet masquerading in BPF. If an
egressing netdev to which the Cilium's BPF prog is attached has
multiple IP addresses, then only one [hardcoded] IP address can be used for
masquerading. This breaks connectivity if any other IP address should have
been selected instead, for example, when a public and private addresses
are attached to the same egress interface.

The change was tested with Cilium [1].

Nikolay Aleksandrov helped to figure out the IPv6 addr selection.

[1]: https://github.com/cilium/cilium/pull/28283

Signed-off-by: Martynas Pumputis <m@lambda.lt>
Link: https://lore.kernel.org/r/20231007081415.33502-2-m@lambda.lt
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-03-06 14:38:50 +00:00
arch x86/cpu/intel: Detect TME keyid bits before setting MTRR mask registers 2024-03-06 14:38:49 +00:00
block blk-iocost: Fix an UBSAN shift-out-of-bounds warning 2024-02-23 08:54:59 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: api - Disallow identical driver names 2024-02-23 08:54:23 +01:00
Documentation platform/x86: asus-wmi: Document the dgpu_disable sysfs attribute 2024-03-01 13:21:52 +01:00
drivers Revert "interconnect: Teach lockdep about icc_bw_lock order" 2024-03-06 14:38:50 +00:00
fs fs,hugetlb: fix NULL pointer dereference in hugetlbs_fill_super 2024-03-06 14:38:50 +00:00
include bpf: Derive source IP addr via bpf_*_fib_lookup() 2024-03-06 14:38:50 +00:00
init rootfs: Fix support for rootfstype= when root= is given 2024-01-25 14:52:48 -08:00
io_uring io_uring/rw: ensure io->bytes_done is always initialized 2024-01-25 14:52:48 -08:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel bpf: Fix racing between bpf_timer_cancel_and_free and bpf_timer_cancel 2024-03-01 13:21:59 +01:00
lib debugobjects: Recheck debug_objects_enabled before reporting 2024-03-01 13:21:54 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm userfaultfd: fix mmap_changing checking in mfill_atomic_hugetlb 2024-03-01 13:21:43 +01:00
net bpf: Derive source IP addr via bpf_*_fib_lookup() 2024-03-06 14:38:50 +00:00
samples samples/hw_breakpoint: fix building without module unloading 2023-09-23 11:10:01 +02:00
scripts bpf, scripts: Correct GPL license name 2024-03-01 13:21:58 +01:00
security tomoyo: fix UAF write bug in tomoyo_write_control() 2024-03-06 14:38:48 +00:00
sound ALSA: firewire-lib: fix to check cycle continuity 2024-03-06 14:38:48 +00:00
tools bpf: Derive source IP addr via bpf_*_fib_lookup() 2024-03-06 14:38:50 +00:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:22:40 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS iio: stx104: Move to addac subdirectory 2023-08-26 14:23:27 +02:00
Makefile Linux 5.15.150 2024-03-01 13:22:01 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 Restructured Text 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.