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Add support for running a container with a private network interface

Browse source 
For example, the following sets up a container named ‘foo’.  The
container will have a single network interface eth0, with IP address
10.231.136.2.  The host will have an interface c-foo with IP address
10.231.136.1.

  systemd.containers.foo =
    { privateNetwork = true;
      hostAddress = "10.231.136.1";
      localAddress = "10.231.136.2";
      config =
        { services.openssh.enable = true; };
    };

With ‘privateNetwork = true’, the container has the CAP_NET_ADMIN
capability, allowing it to do arbitrary network configuration, such as
setting up firewall rules.  This is secure because it cannot touch the
interfaces of the host.

The helper program ‘run-in-netns’ is needed at the moment because ‘ip
netns exec’ doesn't quite do the right thing (it remounts /sys without
bind-mounting the original /sys/fs/cgroups).
This commit is contained in:
Eelco Dolstra 2014-03-18 10:49:25 +01:00
parent ac215779dd
commit 895bcdd1cb
3 changed files with 155 additions and 13 deletions
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50
nixos/modules/virtualisation/run-in-netns.c Normal file
View file

@ -0,0 +1,50 @@
#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sched.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <fcntl.h>
#include <linux/limits.h>
int main(int argc, char * * argv)
{
if (argc < 3) {
fprintf(stderr, "%s: missing arguments\n", argv[0]);
return 1;
}
char nsPath[PATH_MAX];
sprintf(nsPath, "/run/netns/%s", argv[1]);
int fd = open(nsPath, O_RDONLY);
if (fd == -1) {
fprintf(stderr, "%s: opening network namespace: %s\n", argv[0], strerror(errno));
return 1;
}
if (setns(fd, CLONE_NEWNET) == -1) {
fprintf(stderr, "%s: setting network namespace: %s\n", argv[0], strerror(errno));
return 1;
}
umount2(nsPath, MNT_DETACH);
if (unlink(nsPath) == -1) {
fprintf(stderr, "%s: unlinking network namespace: %s\n", argv[0], strerror(errno));
return 1;
}
/* FIXME: Remount /sys so that /sys/class/net reflects the
interfaces visible in the network namespace. This requires
bind-mounting /sys/fs/cgroups etc. */
execv(argv[2], argv + 2);
fprintf(stderr, "%s: running command: %s\n", argv[0], strerror(errno));
return 1;
}