From dd2ce6a5373c6f5c830be54be10775458a8bd312 Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Sun, 11 Oct 2020 01:40:01 +0200 Subject: [PATCH] bpf: Improve bpf_redirect_neigh helper description Follow-up to address David's feedback that we should better describe internals of the bpf_redirect_neigh() helper. Suggested-by: David Ahern Signed-off-by: Daniel Borkmann Signed-off-by: Alexei Starovoitov Reviewed-by: David Ahern Link: https://lore.kernel.org/bpf/20201010234006.7075-2-daniel@iogearbox.net --- include/uapi/linux/bpf.h | 10 +++++++--- tools/include/uapi/linux/bpf.h | 10 +++++++--- 2 files changed, 14 insertions(+), 6 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 42d2df799397..4272cc53d478 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3679,10 +3679,14 @@ union bpf_attr { * Redirect the packet to another net device of index *ifindex* * and fill in L2 addresses from neighboring subsystem. This helper * is somewhat similar to **bpf_redirect**\ (), except that it - * fills in e.g. MAC addresses based on the L3 information from - * the packet. This helper is supported for IPv4 and IPv6 protocols. + * populates L2 addresses as well, meaning, internally, the helper + * performs a FIB lookup based on the skb's networking header to + * get the address of the next hop and then relies on the neighbor + * lookup for the L2 address of the nexthop. + * * The *flags* argument is reserved and must be 0. The helper is - * currently only supported for tc BPF program types. + * currently only supported for tc BPF program types, and enabled + * for IPv4 and IPv6 protocols. * Return * The helper returns **TC_ACT_REDIRECT** on success or * **TC_ACT_SHOT** on error. diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 42d2df799397..4272cc53d478 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -3679,10 +3679,14 @@ union bpf_attr { * Redirect the packet to another net device of index *ifindex* * and fill in L2 addresses from neighboring subsystem. This helper * is somewhat similar to **bpf_redirect**\ (), except that it - * fills in e.g. MAC addresses based on the L3 information from - * the packet. This helper is supported for IPv4 and IPv6 protocols. + * populates L2 addresses as well, meaning, internally, the helper + * performs a FIB lookup based on the skb's networking header to + * get the address of the next hop and then relies on the neighbor + * lookup for the L2 address of the nexthop. + * * The *flags* argument is reserved and must be 0. The helper is - * currently only supported for tc BPF program types. + * currently only supported for tc BPF program types, and enabled + * for IPv4 and IPv6 protocols. * Return * The helper returns **TC_ACT_REDIRECT** on success or * **TC_ACT_SHOT** on error. -- GitLab