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Subject: Re: [PATCH] bpf: synchronize bpf uapi header with tools
To:     Taeung Song <treeze.taeung@gmail.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        David Ahern <dsahern@gmail.com>
References: <20180719125355.26441-1-treeze.taeung@gmail.com>
From:   Quentin Monnet <quentin.monnet@netronome.com>
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Date:   Thu, 19 Jul 2018 15:01:26 +0100
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Hi Taeung,

2018-07-19 21:53 UTC+0900 ~ Taeung Song <treeze.taeung@gmail.com>
> To pick the change in:
> 
>   4c79579b44b1 ("bpf: Change bpf_fib_lookup to return lookup status")
> 
> This bpftool build warning occurs:
> 
>   Warning: Kernel ABI header at 'tools/include/uapi/linux/bpf.h' differs from latest version at 'include/uapi/linux/bpf.h'
> 
> Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
> Cc: David Ahern <dsahern@gmail.com>
> Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
> ---
>  tools/include/uapi/linux/bpf.h | 28 +++++++++++++++++++++++-----
>  1 file changed, 23 insertions(+), 5 deletions(-)
> 
> diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
> index 59b19b6a40d7..b7db3261c62d 100644
> --- a/tools/include/uapi/linux/bpf.h
> +++ b/tools/include/uapi/linux/bpf.h
> @@ -1857,7 +1857,8 @@ union bpf_attr {
>   *		is resolved), the nexthop address is returned in ipv4_dst
>   *		or ipv6_dst based on family, smac is set to mac address of
>   *		egress device, dmac is set to nexthop mac address, rt_metric
> - *		is set to metric from route (IPv4/IPv6 only).
> + *		is set to metric from route (IPv4/IPv6 only), and ifindex
> + *		is set to the device index of the nexthop from the FIB lookup.
>   *
>   *             *plen* argument is the size of the passed in struct.
>   *             *flags* argument can be a combination of one or more of the
> @@ -1873,9 +1874,10 @@ union bpf_attr {
>   *             *ctx* is either **struct xdp_md** for XDP programs or
>   *             **struct sk_buff** tc cls_act programs.
>   *     Return
> - *             Egress device index on success, 0 if packet needs to continue
> - *             up the stack for further processing or a negative error in case
> - *             of failure.
> + *		* < 0 if any input argument is invalid
> + *		*   0 on success (packet is forwarded, nexthop neighbor exists)
> + *		* > 0 one of **BPF_FIB_LKUP_RET_** codes explaining why the
> + *		*     packet is not forwarded or needs assist from full stack
>   *
>   * int bpf_sock_hash_update(struct bpf_sock_ops_kern *skops, struct bpf_map *map, void *key, u64 flags)
>   *	Description
> @@ -2612,6 +2614,18 @@ struct bpf_raw_tracepoint_args {
>  #define BPF_FIB_LOOKUP_DIRECT  BIT(0)
>  #define BPF_FIB_LOOKUP_OUTPUT  BIT(1)
>  
> +enum {
> +	BPF_FIB_LKUP_RET_SUCCESS,      /* lookup successful */
> +	BPF_FIB_LKUP_RET_BLACKHOLE,    /* dest is blackholed; can be dropped */
> +	BPF_FIB_LKUP_RET_UNREACHABLE,  /* dest is unreachable; can be dropped */
> +	BPF_FIB_LKUP_RET_PROHIBIT,     /* dest not allowed; can be dropped */
> +	BPF_FIB_LKUP_RET_NOT_FWDED,    /* packet is not forwarded */
> +	BPF_FIB_LKUP_RET_FWD_DISABLED, /* fwding is not enabled on ingress */
> +	BPF_FIB_LKUP_RET_UNSUPP_LWT,   /* fwd requires encapsulation */
> +	BPF_FIB_LKUP_RET_NO_NEIGH,     /* no neighbor entry for nh */
> +	BPF_FIB_LKUP_RET_FRAG_NEEDED,  /* fragmentation required to fwd */
> +};
> +
>  struct bpf_fib_lookup {
>  	/* input:  network family for lookup (AF_INET, AF_INET6)
>  	 * output: network family of egress nexthop
> @@ -2625,7 +2639,11 @@ struct bpf_fib_lookup {
>  
>  	/* total length of packet from network header - used for MTU check */
>  	__u16	tot_len;
> -	__u32	ifindex;  /* L3 device index for lookup */
> +
> +	/* input: L3 device index for lookup
> +	 * output: device index from FIB lookup
> +	 */
> +	__u32	ifindex;
>  
>  	union {
>  		/* inputs to lookup */
> 

This has been updated in the bpf-next tree already, see commit
9b8ca3795199 ("tools: bpf: synchronise BPF UAPI header with tools").

Best regards,
Quentin