netdev - Re: [PATCH bpf v2 1/3] bpf_redirect_neigh: Support supplying the nexthop as a helper parameter

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 20 Oct 2020 12:12:32 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        Toke Høiland-Jørgensen 
        <toke@...hat.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: Re: [PATCH bpf v2 1/3] bpf_redirect_neigh: Support supplying the
 nexthop as a helper parameter

On 10/20/20 10:30 AM, Jakub Kicinski wrote:
> On Tue, 20 Oct 2020 12:51:02 +0200 Toke Høiland-Jørgensen wrote:
>> diff --git a/include/linux/filter.h b/include/linux/filter.h
>> index 20fc24c9779a..ba9de7188cd0 100644
>> --- a/include/linux/filter.h
>> +++ b/include/linux/filter.h
>> @@ -607,12 +607,21 @@ struct bpf_skb_data_end {
>>  	void *data_end;
>>  };
>>  
>> +struct bpf_nh_params {
>> +	u8 nh_family;
>> +	union {
>> +		__u32 ipv4_nh;
>> +		struct in6_addr ipv6_nh;
>> +	};
>> +};
> 
>> @@ -4906,6 +4910,18 @@ struct bpf_fib_lookup {
>>  	__u8	dmac[6];     /* ETH_ALEN */
>>  };
>>  
>> +struct bpf_redir_neigh {
>> +	/* network family for lookup (AF_INET, AF_INET6) */
>> +	__u8 nh_family;
>> +	 /* avoid hole in struct - must be set to 0 */
>> +	__u8 unused[3];
>> +	/* network address of nexthop; skips fib lookup to find gateway */
>> +	union {
>> +		__be32		ipv4_nh;
>> +		__u32		ipv6_nh[4];  /* in6_addr; network order */
>> +	};
>> +};
> 
> Isn't this backward? The hole could be named in the internal structure.
> This is a bit of a gray area, but if you name this hole in uAPI and
> programs start referring to it you will never be able to reuse it.
> So you may as well not require it to be zeroed..
> 

for uapi naming the holes, stating they are unused and requiring a 0
value allows them to be used later if an api change needs to.