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libnetwork/etchosts: add host.containers.internal for machine #2464

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Merged
openshift-merge-bot merged 1 commit into from
Jul 7, 2025
Merged

libnetwork/etchosts: add host.containers.internal for machine #2464

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9 changes: 4 additions & 5 deletions docs/containers.conf.5.md
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Original file line number Diff line number Diff line change
Expand Up @@ -226,11 +226,10 @@ setup. Adding these internal hostnames to `/etc/hosts` is silently skipped then.
Set this config to `none` to never add the internal hostnames to `/etc/hosts`.

Note: If Podman is running in a virtual machine using `podman machine` (this
includes Mac and Windows hosts), Podman will silently skip adding the internal
hostnames to `/etc/hosts`, unless an IP address was configured manually. The
internal hostnames are resolved by the gvproxy DNS resolver instead. This config
has no effect on gvproxy. However, since `/etc/hosts` bypasses the DNS resolver,
a manually configured IP address still takes precedence.
includes Mac and Windows hosts), Podman resolves the `host.containers.internal`
hostname via the podman machine (gvproxy) DNS resolver instead when it is empty.
Also because the name will be resolved by the DNS name in gvproxy setting this
to `none` has no effect. This option does not change the gvproxy behavior.

Note: This config doesn't affect the actual network setup, it just tells Podman
the IP address it should expect. Configuring an IP address here doesn't ensure
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24 changes: 21 additions & 3 deletions libnetwork/etchosts/ip.go
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Expand Up @@ -2,12 +2,14 @@ package etchosts

import (
"net"
"sync"

"github.com/containers/common/libnetwork/types"
"github.com/containers/common/libnetwork/util"
"github.com/containers/common/pkg/config"
"github.com/containers/common/pkg/machine"
"github.com/containers/storage/pkg/unshare"
"github.com/sirupsen/logrus"
)

// HostContainersInternalOptions contains the options for GetHostContainersInternalIP()
Expand All @@ -28,14 +30,30 @@ type HostContainersInternalOptions struct {
PreferIP string
}

// Lookup "host.containers.internal" dns name so we can add it to /etc/hosts when running inside podman machine.
var machineHostContainersInternalIP = sync.OnceValue(func() string {
var errMsg string
addrs, err := net.LookupIP(HostContainersInternal)
if err == nil {
if len(addrs) > 0 {
return addrs[0].String()
}
errMsg = "lookup result is empty"
} else {
errMsg = err.Error()
}
logrus.Warnf("Failed to resolve %s for the host entry ip address: %s", HostContainersInternal, errMsg)
return ""
})

// GetHostContainersInternalIP returns the host.containers.internal ip
func GetHostContainersInternalIP(opts HostContainersInternalOptions) string {
switch opts.Conf.Containers.HostContainersInternalIP {
case "":
// if empty (default) we will automatically choose one below
// if machine using gvproxy we let the gvproxy dns server handle the dns name so do not add it
// If empty (default) we will automatically choose one below.
// If machine using gvproxy we let the gvproxy dns server handle resolve the name and then use that ip.
if machine.IsGvProxyBased() {
return ""
return machineHostContainersInternalIP()
}
case "none":
return ""
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