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bpf: Change bpf_fib_lookup to return lookup status

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For ACLs implemented using either FIB rules or FIB entries, the BPF
program needs the FIB lookup status to be able to drop the packet.
Since the bpf_fib_lookup API has not reached a released kernel yet,
change the return code to contain an encoding of the FIB lookup
result and return the nexthop device index in the params struct.

In addition, inform the BPF program of any post FIB lookup reason as
to why the packet needs to go up the stack.

The fib result for unicast routes must have an egress device, so remove
the check that it is non-NULL.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
David Ahern
2018-06-26 16:21:18 -07:00
committed by Daniel Borkmann
parent 3203c90100
commit 4c79579b44
3 changed files with 81 additions and 41 deletions
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8
samples/bpf/xdp_fwd_kern.c
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@@ -48,9 +48,9 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags)
struct ethhdr *eth = data;
struct ipv6hdr *ip6h;
struct iphdr *iph;
int out_index;
u16 h_proto;
u64 nh_off;
int rc;
nh_off = sizeof(*eth);
if (data + nh_off > data_end)
@@ -101,7 +101,7 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags)
fib_params.ifindex = ctx->ingress_ifindex;
out_index = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags);
rc = bpf_fib_lookup(ctx, &fib_params, sizeof(fib_params), flags);
/* verify egress index has xdp support
* TO-DO bpf_map_lookup_elem(&tx_port, &key) fails with
@@ -109,7 +109,7 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags)
* NOTE: without verification that egress index supports XDP
* forwarding packets are dropped.
*/
if (out_index > 0) {
if (rc == 0) {
if (h_proto == htons(ETH_P_IP))
ip_decrease_ttl(iph);
else if (h_proto == htons(ETH_P_IPV6))
@@ -117,7 +117,7 @@ static __always_inline int xdp_fwd_flags(struct xdp_md *ctx, u32 flags)
memcpy(eth->h_dest, fib_params.dmac, ETH_ALEN);
memcpy(eth->h_source, fib_params.smac, ETH_ALEN);
return bpf_redirect_map(&tx_port, out_index, 0);
return bpf_redirect_map(&tx_port, fib_params.ifindex, 0);
}
return XDP_PASS;