Re: [coLinux-users] change in slirp behavior from 0.7.1 to 0.7.3 with udp forwarded ports

[Henry N. <hen...@ar...>]

Henry Nestler wrote:
> Hello Mike,
> 
> Mike Frysinger wrote:
>> On Sun, Jun 22, 2008 at 4:59 PM, Henry Nestler wrote:
>>> The difference for coLinux 0.7.1 and 0.7.3 are very small. Mostly are
>>> fixups for compiler warnings.
>>>
>>> There exist an other interesting change between versions:
>>> http://colinux.svn.sourceforge.net/viewvc/colinux?view=rev&revision=574
>> so there may be a discrepancy when i said "0.7.1".  i was given an old
>> coLinux installer and was told it was "0.7.1".  i assumed everything
>> in the package was "0.7.1"; the person before me may have taken an
>> older slirp daemon and dropped it in for this same reason.  so as to
>> make things maintainable, i started fresh with the 0.7.3 release from
>> colinux.org, hit this bug, and then copied the slirp daemon from this
>> "0.7.1" version.
>>
>> so let's just focus on the svn info i posted otherwise as that is used
>> in conjunction with vanilla 0.7.3 install without any unknown baggage.
>>  sorry for any confusion.
>> -mike
>>
> 
> With rev 479/480 you pointed to a bigger set of changes.
> 
> By the while I found the place where it goes wrong. Please see the
> source snip or:
> http://colinux.svn.sourceforge.net/viewvc/colinux/branches/devel/src/colinux/user/slirp/udp.c?revision=677&view=markup
> 
> file udp.c, line 323, function udp_output()
> 
> In the line 323 the source address saddr.sin_addr (192.168.x.x) is
> overwritten with 10.0.2.2
> One line before was checked the listen address (so->so_faddr).
> I'm afraid, there should check the source address instead? But why there
> is a check for broadcast? Is that a hack for a hack? It sems me, that it
> would better work without the lines from 322 to 326 there?
> 
> Background:
> special_addr = 10.0.2.2 (const)

Typofix. That is correctly:
special_addr = 10.0.2.0 (const)
alias_addr = 10.0.2.2 (const)

> 
> All UDP sockets are listen on address 0.0.0.0, that address is set as
> faked address 10.0.2.2 in line 383:
> "so->so_faddr = alias_addr;"
> 
> -----------------------------------
> devel/src/colinux/user/slirp/udp.c
>   315 int udp_output(struct socket *so, struct mbuf *m,
>   316                struct sockaddr_in *addr)
>   317
>   318 {
>   319     struct sockaddr_in saddr, daddr;
>   320
>   321     saddr = *addr;
>   322     if ((so->so_faddr.s_addr & htonl(0xffffff00)) ==
> special_addr.s_addr) {
>   323         saddr.sin_addr.s_addr = so->so_faddr.s_addr;
>   324         if ((so->so_faddr.s_addr & htonl(0x000000ff)) == htonl(0xff))
>   325             saddr.sin_addr.s_addr = alias_addr.s_addr;
>   326     }
>   327     daddr.sin_addr = so->so_laddr;
>   328     daddr.sin_port = so->so_lport;
>   329
>   330     return udp_output2(so, m, &saddr, &daddr, so->so_iptos);
>   331 }
> 

-- 
Henry N.