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Use the slrip4netns dns in the rootless cni ns 

If a user only has a local dns server in the resolv.conf file the dns
resolution will fail. Instead we create a new resolv.conf which will use
the slirp4netns dns.

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>
This commit is contained in:
Paul Holzinger 2021-03-26 10:41:01 +01:00
parent 6cd807e3b7
commit 973807092d
1 changed files with 31 additions and 2 deletions
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33
libpod/networking_linux.go
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@ -24,6 +24,7 @@ import (
"github.com/containers/podman/v3/libpod/network"
"github.com/containers/podman/v3/pkg/errorhandling"
"github.com/containers/podman/v3/pkg/netns"
"github.com/containers/podman/v3/pkg/resolvconf"
"github.com/containers/podman/v3/pkg/rootless"
"github.com/containers/podman/v3/pkg/util"
"github.com/containers/storage/pkg/lockfile"
@ -134,9 +135,14 @@ func (r *rootlessCNI) Do(toRun func() error) error {
return errors.Wrap(err, "failed to mount netns directory for rootless cni")
}
// mount resolv.conf to make use of the host dns
err = unix.Mount(filepath.Join(r.dir, "resolv.conf"), "/etc/resolv.conf", "none", unix.MS_BIND, "")
if err != nil {
return errors.Wrap(err, "failed to mount resolv.conf for rootless cni")
}
// also keep /run/systemd if it exists
// many files are symlinked into this dir, for example systemd-resolved links
// /etc/resolv.conf but the dnsname plugin needs access to this file
// many files are symlinked into this dir, for example /dev/log
runSystemd := "/run/systemd"
_, err = os.Stat(runSystemd)
if err == nil {
@ -348,6 +354,29 @@ func (r *Runtime) getRootlessCNINetNs(new bool) (*rootlessCNI, error) {
return nil, err
}
// build a new resolv.conf file which uses the slirp4netns dns server address
resolveIP := slirp4netnsDNS
if netOptions.cidr != "" {
_, cidr, err := net.ParseCIDR(netOptions.cidr)
if err != nil {
return nil, errors.Wrap(err, "failed to parse slirp4netns cidr")
}
// the slirp dns ip is always the third ip in the subnet
cidr.IP[len(cidr.IP)-1] = cidr.IP[len(cidr.IP)-1] + 3
resolveIP = cidr.IP.String()
}
conf, err := resolvconf.Get()
if err != nil {
return nil, err
}
searchDomains := resolvconf.GetSearchDomains(conf.Content)
dnsOptions := resolvconf.GetOptions(conf.Content)
_, err = resolvconf.Build(filepath.Join(cniDir, "resolv.conf"), []string{resolveIP}, searchDomains, dnsOptions)
if err != nil {
return nil, errors.Wrap(err, "failed to create rootless cni resolv.conf")
}
// create cni directories to store files
// they will be bind mounted to the correct location in a extra mount ns
err = os.MkdirAll(filepath.Join(cniDir, "var"), 0700)