Re: make it easier to configure IPv6 on gif(4)

[Sebastian Benoit]

ok

Stefan Sperling(s...@stsp.name) on 2017.06.24 07:09:20 +0200:
> The kernel rejects IPv6 destination addresses on point-to-point
> interfaces if the prefixlen is not 128. Because ifconfig defaults
> to prefixlen 64, configuring IPv6 on e.g. gif(4) requires an
> explicit prefix length, for instance:
> 
>ifconfig gif0 inet6 ADDR1 ADDR2 prefixlen 128
> 
> Without prefixlen we get: ifconfig: SIOCAIFADDR: Invalid argument
> 
> However, this command works for IPv4:
> 
>ifconfig gif0 ADDR1 ADDR2
> 
> The netmask isn't forced to 255.255.255.255 by the kernel, though.
> 
> Assuming the kernel is correct in enforcing IPv6 prefixlen 128,
> for whatever reason, then I suggest we make ifconfig figure out
> the required prefixlen by itself so this command works as it
> does for IPv4:
> 
>ifconfig gif0 inet6 ADDR1 ADDR2
> 
> ok?
> 
> Index: ifconfig.c
> ===
> RCS file: /cvs/src/sbin/ifconfig/ifconfig.c,v
> retrieving revision 1.344
> diff -u -p -r1.344 ifconfig.c
> --- ifconfig.c8 Jun 2017 19:23:39 -   1.344
> +++ ifconfig.c24 Jun 2017 04:54:17 -
> @@ -803,9 +803,13 @@ nextarg:
>   /*
>* Aggregatable address architecture defines all prefixes
>* are 64. So, it is convenient to set prefixlen to 64 if
> -  * it is not specified.
> +  * it is not specified. If we are setting a destination
> +  * address on a point-to-point interface, 128 is required.
>*/
> - setifprefixlen("64", 0);
> + if (setipdst && (flags & IFF_POINTOPOINT))
> + setifprefixlen("128", 0);
> + else
> + setifprefixlen("64", 0);
>   /* in6_getprefix("64", MASK) if MASK is available here... */
>   }
>  
> @@ -1241,6 +1245,7 @@ void
>  setifdstaddr(const char *addr, int param)
>  {
>   setaddr++;
> + setipdst++;
>   afp->af_getaddr(addr, DSTADDR);
>  }
>  
> 

Re: make it easier to configure IPv6 on gif(4)

[Alexander Bluhm]

On Sat, Jun 24, 2017 at 07:09:20AM +0200, Stefan Sperling wrote:
> ok?

OK bluhm@

> 
> Index: ifconfig.c
> ===
> RCS file: /cvs/src/sbin/ifconfig/ifconfig.c,v
> retrieving revision 1.344
> diff -u -p -r1.344 ifconfig.c
> --- ifconfig.c8 Jun 2017 19:23:39 -   1.344
> +++ ifconfig.c24 Jun 2017 04:54:17 -
> @@ -803,9 +803,13 @@ nextarg:
>   /*
>* Aggregatable address architecture defines all prefixes
>* are 64. So, it is convenient to set prefixlen to 64 if
> -  * it is not specified.
> +  * it is not specified. If we are setting a destination
> +  * address on a point-to-point interface, 128 is required.
>*/
> - setifprefixlen("64", 0);
> + if (setipdst && (flags & IFF_POINTOPOINT))
> + setifprefixlen("128", 0);
> + else
> + setifprefixlen("64", 0);
>   /* in6_getprefix("64", MASK) if MASK is available here... */
>   }
>  
> @@ -1241,6 +1245,7 @@ void
>  setifdstaddr(const char *addr, int param)
>  {
>   setaddr++;
> + setipdst++;
>   afp->af_getaddr(addr, DSTADDR);
>  }
>  

make it easier to configure IPv6 on gif(4)

[Stefan Sperling]

The kernel rejects IPv6 destination addresses on point-to-point
interfaces if the prefixlen is not 128. Because ifconfig defaults
to prefixlen 64, configuring IPv6 on e.g. gif(4) requires an
explicit prefix length, for instance:

   ifconfig gif0 inet6 ADDR1 ADDR2 prefixlen 128

Without prefixlen we get: ifconfig: SIOCAIFADDR: Invalid argument

However, this command works for IPv4:

   ifconfig gif0 ADDR1 ADDR2

The netmask isn't forced to 255.255.255.255 by the kernel, though.

Assuming the kernel is correct in enforcing IPv6 prefixlen 128,
for whatever reason, then I suggest we make ifconfig figure out
the required prefixlen by itself so this command works as it
does for IPv4:

   ifconfig gif0 inet6 ADDR1 ADDR2

ok?

Index: ifconfig.c
===
RCS file: /cvs/src/sbin/ifconfig/ifconfig.c,v
retrieving revision 1.344
diff -u -p -r1.344 ifconfig.c
--- ifconfig.c  8 Jun 2017 19:23:39 -   1.344
+++ ifconfig.c  24 Jun 2017 04:54:17 -
@@ -803,9 +803,13 @@ nextarg:
/*
 * Aggregatable address architecture defines all prefixes
 * are 64. So, it is convenient to set prefixlen to 64 if
-* it is not specified.
+* it is not specified. If we are setting a destination
+* address on a point-to-point interface, 128 is required.
 */
-   setifprefixlen("64", 0);
+   if (setipdst && (flags & IFF_POINTOPOINT))
+   setifprefixlen("128", 0);
+   else
+   setifprefixlen("64", 0);
/* in6_getprefix("64", MASK) if MASK is available here... */
}
 
@@ -1241,6 +1245,7 @@ void
 setifdstaddr(const char *addr, int param)
 {
setaddr++;
+   setipdst++;
afp->af_getaddr(addr, DSTADDR);
 }