b96f500dbb
commit dab4e1f06cabb6834de14264394ccab197007302 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>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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|---|---|---|
| .. | ||
| tc_act | ||
| bpf_common.h | ||
| bpf_perf_event.h | ||
| bpf.h | ||
| btf.h | ||
| const.h | ||
| erspan.h | ||
| ethtool.h | ||
| fadvise.h | ||
| fcntl.h | ||
| filter.h | ||
| fs.h | ||
| fscrypt.h | ||
| hw_breakpoint.h | ||
| if_link.h | ||
| if_tun.h | ||
| if_xdp.h | ||
| in.h | ||
| kcmp.h | ||
| kvm.h | ||
| mman.h | ||
| mount.h | ||
| netdev.h | ||
| netlink.h | ||
| openat2.h | ||
| perf_event.h | ||
| pkt_cls.h | ||
| pkt_sched.h | ||
| prctl.h | ||
| sched.h | ||
| seccomp.h | ||
| seg6_local.h | ||
| seg6.h | ||
| stat.h | ||
| stddef.h | ||
| tcp.h | ||
| tls.h | ||
| types.h | ||
| usbdevice_fs.h | ||
| vhost.h | ||