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Message-ID: <20240816170034.GT10433@brightrain.aerifal.cx>
Date: Fri, 16 Aug 2024 13:00:35 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: libc-test contribution
On Fri, Aug 16, 2024 at 11:57:29AM -0400, Rich Felker wrote:
> On Fri, Aug 16, 2024 at 09:35:38AM +0200, Szabolcs Nagy wrote:
> > * Ward, Ryan C <ryan.c.ward3@...ing.com> [2024-08-16 01:06:55 +0000]:
> > > Hello,
> > >
> > > I would like to start contributing some test cases to libc-test. I have
> > > started with testing some simple recent regressions (e.g. a test for
> > > the recent fix commit 947b4574), and am aiming to start filling in
> > > missing functional test coverage. Am I able to submit the test
> > > directly to this mailing list, and are there any other immediate
> > > areas of libc-test that need implementation?
> >
> > this list is fine
> >
> > there are many areas missing
> > but they need test infrastucture
> > eg networking tests depending on
> > /etc/resolv.conf need to run in
> > a separate mount namespace.
>
> I could try writing a helper module to do this. Basically it would
> just unshare into a new user+mount+network namespace and, if
> /etc/resolv.conf exists, bind-mount an empty file over it. Then you
> can bind port 53 and it will intercept all queries, and you don't have
> to worry about anything going out to the real network or having
> network-dependent behaviors.
Something like this:
#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <sched.h>
#include <sys/mount.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <netinet/in.h>
int enter_dns_test_ns()
{
if (unshare(CLONE_NEWUSER|CLONE_NEWNS|CLONE_NEWNET) < 0)
return -1;
int s = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
if (s < 0) return -1;
struct ifreq ifr = {
.ifr_name = "lo",
.ifr_addr = (union { struct sockaddr_in sin; struct sockaddr sa; }){{
.sin_family = AF_INET,
.sin_port = 0,
.sin_addr = htonl(0x7f000001),
}}.sa,
};
if (ioctl(s, SIOCSIFADDR, &ifr) < 0)
return -1;
if (ioctl(s, SIOCGIFFLAGS, &ifr) < 0)
return -1;
ifr.ifr_flags |= IFF_UP;
if (ioctl(s, SIOCSIFFLAGS, &ifr) < 0)
return -1;
char tmp[] = "/tmp/emptyXXXXXX";
int fd = mkostemp(tmp, O_CLOEXEC);
if (fd < 0) return -1;
int r = mount(tmp, "/etc/resolv.conf", 0, MS_BIND, 0);
unlink(tmp);
return r;
}
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