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Date: Thu, 18 Jun 2009 09:57:30 +0200
To: =?utf-8?Q?Fr=C3=A9d=C3=A9ric_Bron?= <frederic DOT bron AT m4x DOT org>,
   cygwin  <cygwin AT cygwin DOT com>
Subject: Re: ioctl(sock, SIOCGIFHWADDR, &ifr) fails with 1.7
From: "Matthias Andree" <matthias DOT andree AT gmx DOT de>
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Am 15.06.2009, 11:22 Uhr, schrieb Frédéric Bron <frederic DOT bron AT m4x DOT org>:

>> To fix your application, call either
>>
>>  struct ifconf ifc;
>>  ifc.ifc_len = sizeof (struct ifreq) * 32;
>>  ifc.ifc_buf = malloc (ifc.ifc_len);
>>  if (ioctl (fd, SIOCGIFCONF, &ifc))
>>    /* Resize ifc_buf and retry */
>>  else
>>    {
>>      struct ifreq *ifr = ifc.ifc_req;
>>      struct ifreq ifr2;
>>      for (int i = 0; i < ifc.ifc_len; i += sizeof (struct ifreq), ++ifr)
>>        if (!ioctl (fd, SIOCGIFADDR, &ifr2))
>>          /* Print result for that interface */
>>    }
>
> Thanks, this works half! No need of ifr2, ifr is enough.
> I saw the name change: 1.5 gives eth0, eth1, eth2, lo and 1.7 gives
> {821C54BE-...}...

Careful - this isn't portable to newer BSDs, as there ifc_len may exceed  
sizeof(struct ifreq).

getifaddrs() is probably the more portable solution here.

-- 
Matthias Andree

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