libnetwork: Add support for host-gateway

This change adds support for the special IP designator `host-gateway` to the etchosts package. The first part of fixing containers/podman#14390 Signed-off-by: Gregor Eichelberger <[email protected]>
geichelberger · Jul 6, 2023 · 6674663 · 6674663
1 parent 2b3ce8f
commit 6674663
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Showing 2 changed files with 14 additions and 3 deletions.
diff --git a/libnetwork/etchosts/hosts.go b/libnetwork/etchosts/hosts.go
@@ -98,7 +98,7 @@ func Remove(file string, entries HostEntries) error {
 
 // new see comment on New()
 func newHost(params *Params) error {
-	entries, err := parseExtraHosts(params.ExtraHosts)
+	entries, err := parseExtraHosts(params.ExtraHosts, params.HostContainersInternalIP)
 	if err != nil {
 		return err
 	}
@@ -230,7 +230,7 @@ func checkIfEntryExists(current HostEntry, entries HostEntries) bool {
 // parseExtraHosts converts a slice of "name:ip" string to entries.
 // Because podman and buildah both store the extra hosts in this format
 // we convert it here instead of having to this on the caller side.
-func parseExtraHosts(extraHosts []string) (HostEntries, error) {
+func parseExtraHosts(extraHosts []string, hostContainersInternalIP string) (HostEntries, error) {
 	entries := make(HostEntries, 0, len(extraHosts))
 	for _, entry := range extraHosts {
 		values := strings.SplitN(entry, ":", 2)
@@ -243,7 +243,11 @@ func parseExtraHosts(extraHosts []string) (HostEntries, error) {
 		if values[1] == "" {
 			return nil, fmt.Errorf("IP address in host entry %q is empty", entry)
 		}
-		e := HostEntry{IP: values[1], Names: []string{values[0]}}
+		ip := values[1]
+		if values[1] == "host-gateway" {
+			ip = hostContainersInternalIP
+		}
+		e := HostEntry{IP: ip, Names: []string{values[0]}}
 		entries = append(entries, e)
 	}
 	return entries, nil

diff --git a/libnetwork/etchosts/hosts_test.go b/libnetwork/etchosts/hosts_test.go
@@ -218,6 +218,13 @@ func TestNew(t *testing.T) {
 			hostContainersInternal:    "10.0.0.1",
 			expectedTargetFileContent: targetFileContent1 + "10.0.0.1\thost.containers.internal\n",
 		},
+		{
+			name:                      "with host.containers.internal ip and host-gateway",
+			baseFileContent:           baseFileContent1Spaces,
+			extraHosts:                []string{"gatewayname:host-gateway"},
+			hostContainersInternal:    "10.0.0.1",
+			expectedTargetFileContent: "10.0.0.1\tgatewayname\n" + targetFileContent1 + "10.0.0.1\thost.containers.internal\n",
+		},
 		{
 			name:                      "host.containers.internal not added when already present in extra hosts",
 			baseFileContent:           baseFileContent1Spaces,