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authorMartynas Pumputis <m@lambda.lt>2023-10-07 11:14:14 +0300
committerMartin KaFai Lau <martin.lau@kernel.org>2023-10-10 02:28:35 +0300
commitdab4e1f06cabb6834de14264394ccab197007302 (patch)
treec5b6fa4aafbea4a32b0891e17b31647179939729 /net/ipv6
parent1be84ca53ca0421c781f9ec007cd8bccbb58f763 (diff)
downloadlinux-dab4e1f06cabb6834de14264394ccab197007302.tar.xz
bpf: Derive source IP addr via bpf_*_fib_lookup()
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>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/af_inet6.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index c6ad0d6e99b5..6337fb4504fd 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -1061,6 +1061,7 @@ static const struct ipv6_bpf_stub ipv6_bpf_stub_impl = {
.udp6_lib_lookup = __udp6_lib_lookup,
.ipv6_setsockopt = do_ipv6_setsockopt,
.ipv6_getsockopt = do_ipv6_getsockopt,
+ .ipv6_dev_get_saddr = ipv6_dev_get_saddr,
};
static int __init inet6_init(void)