On 05/01/14 15:04, Marek Lindner wrote:
> On Sunday 05 January 2014 09:59:52 Antonio Quartulli wrote:
>> @@ -528,7 +526,7 @@ static int resolve_mac_from_cache_open(int ai_family)
>>         if (ret < 0)
>>                 goto outclose;
>>  
>> -       ret = send(socknl, &nlreq, nlreq.hdr.nlmsg_len, 0);
>> +       ret = send(socknl, req, len, 0);
>>         if (ret < 0)
>>                 goto outclose;
>>  out:
>> @@ -538,6 +536,22 @@ outclose:
>>         return ret;
>>  }
>>  
>> +static int resolve_mac_from_cache_open(int ai_family)
>> +{
>> +       struct {
>> +               struct nlmsghdr hdr;
>> +               struct ndmsg msg;
>> +       } nlreq;
>> +
>> +       memset(&nlreq, 0, sizeof(nlreq));
>> +       nlreq.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(nlreq.msg));
>> +       nlreq.hdr.nlmsg_type = RTM_GETNEIGH;
>> +       nlreq.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
>> +       nlreq.msg.ndm_family = ai_family;
>> +
>> +       return rtnl_open(&nlreq, sizeof(nlreq), NETLINK_ROUTE);
>> +}
> 
> Is 'sizeof(nlreq)' equal to 'nlreq.hdr.nlmsg_len' ? It seems not ...

It is because the macro NLMSG_LENGTH adds NLMSG_HDRLEN to the value
passed as argument (in this case it is sizeof(nlreq.msg)) and therefore
what we store in nlreq.hdr.nlmsg_len is sizeof(nlreq) (plus some
possible alignment bytes).

I think I can make it more clear and always pass nlreq.hdr.nlmsg_len to
send().


Thanks!

v2 is coming!


Cheers,


-- 
Antonio Quartulli