Re: Does FreeBSD stack support multiple IP addresses?

[Grant Edwards <grant dot b dot edwards at gmail dot com>]

On 2016-03-15, Lambrecht JÃrgen <J.Lambrecht@TELEVIC.com> wrote:
> On 02/23/2016 04:59 PM, Grant Edwards wrote:

>> I just re-ran my tests and verified again that I'm able to set the IP
>> and netmask in a single call to ioctl(SIOCAIFADDR).  In my tests, I
>> tried:
>>
>>   Address         Netmask
>> -----------      --------------
>>   11.0.0.104      255.0.0.0
>>   11.0.0.104      255.255.0.0
>>   11.0.0.104      255.255.255.0
>>   11.0.0.104      255.240.0.0

> OK, now I see it: you use
>    SIOCAIFADDR
> we use
>    SIOCSIFADDR
> (from http://sourceware.org/ml/ecos-discuss/2005-08/msg00015.html)

Yes.

> Where did you learn to use SIOCAIFADDR?

When I was writing a DHCPv6 implimentation, I had found some example
code somewhere that used SIOCAIFADDR_IN6.  So, I grepped the stack
source for SIOCAIFADDR.

Below is the function I was using during my testing.  The 's'
parameter is a UDP socket file descriptor.

   void addInterfaceAddress4(int s, uint32_t ip4addr, uint32_t netmask)
   {
     struct in_aliasreq ifra;
     struct sockaddr_in *addrp, *maskp;
   
     memset(&ifra, 0, sizeof ifra);
     strcpy(ifra.ifra_name, "eth0");
   
     addrp = (struct sockaddr_in *)  &ifra.ifra_addr;
     memset(addrp, 0, sizeof(*addrp));
     addrp->sin_family = AF_INET;
     addrp->sin_len = sizeof(*addrp);
     addrp->sin_port = 0;
   
     maskp = (struct sockaddr_in *)  &ifra.ifra_mask;
     memset(maskp, 0, sizeof(*maskp));
     maskp->sin_family = AF_INET;
     maskp->sin_len = sizeof(*maskp);
     maskp->sin_port = 0;
   
     addrp->sin_addr.s_addr = htonl(ip4addr);
     maskp->sin_addr.s_addr = htonl(netmask);
     if (ioctl(s, SIOCAIFADDR, &ifra))
       diag_printf("Error setting second 'eth0' IP address (SIOCAIFADDR): %s\n", strerror(errno));
   }


I just noticed that the memset(addrp,...) and memset(maskp,...) calls
are redundant (not needed).

-- 
Grant Edwards               grant.b.edwards        Yow! ... My pants just went
                                  at               on a wild rampage through a
                              gmail.com            Long Island Bowling Alley!!


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