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bpf: Fix bpf_redirect_neigh helper api to support supplying nexthop

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Based on the discussion in [0], update the bpf_redirect_neigh() helper to
accept an optional parameter specifying the nexthop information. This makes
it possible to combine bpf_fib_lookup() and bpf_redirect_neigh() without
incurring a duplicate FIB lookup - since the FIB lookup helper will return
the nexthop information even if no neighbour is present, this can simply
be passed on to bpf_redirect_neigh() if bpf_fib_lookup() returns
BPF_FIB_LKUP_RET_NO_NEIGH. Thus fix & extend it before helper API is frozen.

  [0] https://lore.kernel.org/bpf/393e17fc-d187-3a8d-2f0d-a627c7c63fca@iogearbox.net/

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/bpf/160322915615.32199.1187570224032024535.stgit@toke.dk
This commit is contained in:
Toke Høiland-Jørgensen
2020-10-20 23:25:56 +02:00
committed by Daniel Borkmann
parent c5eb48e892
commit ba452c9e99
5 changed files with 145 additions and 67 deletions
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22
tools/include/uapi/linux/bpf.h
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@@ -3677,15 +3677,19 @@ union bpf_attr {
* Return
* The id is returned or 0 in case the id could not be retrieved.
*
* long bpf_redirect_neigh(u32 ifindex, u64 flags)
* long bpf_redirect_neigh(u32 ifindex, struct bpf_redir_neigh *params, int plen, u64 flags)
* Description
* 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
* 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.
* relies on the neighbor lookup for the L2 address of the nexthop.
*
* The helper will perform a FIB lookup based on the skb's
* networking header to get the address of the next hop, unless
* this is supplied by the caller in the *params* argument. The
* *plen* argument indicates the len of *params* and should be set
* to 0 if *params* is NULL.
*
* The *flags* argument is reserved and must be 0. The helper is
* currently only supported for tc BPF program types, and enabled
@@ -4906,6 +4910,16 @@ struct bpf_fib_lookup {
__u8 dmac[6]; /* ETH_ALEN */
};
struct bpf_redir_neigh {
/* network family for lookup (AF_INET, AF_INET6) */
__u32 nh_family;
/* network address of nexthop; skips fib lookup to find gateway */
union {
__be32 ipv4_nh;
__u32 ipv6_nh[4]; /* in6_addr; network order */
};
};
enum bpf_task_fd_type {
BPF_FD_TYPE_RAW_TRACEPOINT, /* tp name */
BPF_FD_TYPE_TRACEPOINT, /* tp name */