ipam/host-local: add ResolvConf argument for DNS configuration

This adds the option `resolvConf` to the host-local IPAM configuration.
If specified, the plugin will try to parse the file as a resolv.conf(5)
type file and return it in the DNS response.

Documentation/host-local.md

@@ -30,6 +30,7 @@ It stores the state locally on the host filesystem, therefore ensuring uniquenes
 * `rangeEnd` (string, optional): IP inside of "subnet" with which to end allocating addresses. Defaults to ".254" IP inside of the "subnet" block.
 * `gateway` (string, optional): IP inside of "subnet" to designate as the gateway. Defaults to ".1" IP inside of the "subnet" block.
 * `routes` (string, optional): list of routes to add to the container namespace. Each route is a dictionary with "dst" and optional "gw" fields. If "gw" is omitted, value of "gateway" will be used.
+* `resolvConf` (string, optional): Path to a `resolv.conf` on the host to parse and return as the DNS configuration
 
 ## Supported arguments
 The following [CNI_ARGS](https://github.com/containernetworking/cni/blob/master/SPEC.md#parameters) are supported:

plugins/ipam/host-local/README.md

@@ -1,6 +1,7 @@
 # host-local IP address manager
 
-host-local IPAM allocates IPv4 and IPv6 addresses out of a specified address range.
+host-local IPAM allocates IPv4 and IPv6 addresses out of a specified address range. Optionally,
+it can include a DNS configuration from a `resolv.conf` file on the host.
 
 ## Usage
 
@@ -65,7 +66,8 @@ f81d4fae-7dec-11d0-a765-00a0c91e6bf6
 		"rangeEnd": "3ffe:ffff:0:01ff::0020",
 		"routes": [
 			{ "dst": "3ffe:ffff:0:01ff::1/64" }
-		]
+		],
+		"resolvConf": "/etc/resolv.conf"
 	}
 }
 ```

plugins/ipam/host-local/backend/allocator/config.go

@@ -32,6 +32,7 @@ type IPAMConfig struct {
 	Gateway    net.IP        `json:"gateway"`
 	Routes     []types.Route `json:"routes"`
 	DataDir    string        `json:"dataDir"`
+	ResolvConf string        `json:"resolvConf"`
 	Args       *IPAMArgs     `json:"-"`
 }
 

plugins/ipam/host-local/dns.go

@@ -0,0 +1,64 @@
+// Copyright 2016 CNI authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"bufio"
+	"os"
+	"strings"
+
+	"github.com/containernetworking/cni/pkg/types"
+)
+
+// parseResolvConf parses an existing resolv.conf in to a DNS struct
+func parseResolvConf(filename string) (*types.DNS, error) {
+	fp, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+
+	dns := types.DNS{}
+	scanner := bufio.NewScanner(fp)
+	for scanner.Scan() {
+		line := scanner.Text()
+		line = strings.TrimSpace(line)
+
+		// Skip comments, empty lines
+		if len(line) == 0 || line[0] == '#' || line[0] == ';' {
+			continue
+		}
+
+		fields := strings.Fields(line)
+		if len(fields) < 2 {
+			continue
+		}
+		switch fields[0] {
+		case "nameserver":
+			dns.Nameservers = append(dns.Nameservers, fields[1])
+		case "domain":
+			dns.Domain = fields[1]
+		case "search":
+			dns.Search = append(dns.Search, fields[1:]...)
+		case "options":
+			dns.Options = append(dns.Options, fields[1:]...)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return nil, err
+	}
+
+	return &dns, nil
+}

plugins/ipam/host-local/dns_test.go

@@ -0,0 +1,80 @@
+// Copyright 2016 CNI authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"io/ioutil"
+	"os"
+
+	"github.com/containernetworking/cni/pkg/types"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("parsing resolv.conf", func() {
+	It("parses a simple resolv.conf file", func() {
+		contents := `
+		nameserver 192.0.2.0
+		nameserver 192.0.2.1
+		`
+		dns, err := parse(contents)
+		Expect(err).NotTo(HaveOccurred())
+		Expect(*dns).Should(Equal(types.DNS{Nameservers: []string{"192.0.2.0", "192.0.2.1"}}))
+	})
+	It("ignores comments", func() {
+		dns, err := parse(`
+nameserver 192.0.2.0
+;nameserver 192.0.2.1
+`)
+		Expect(err).NotTo(HaveOccurred())
+		Expect(*dns).Should(Equal(types.DNS{Nameservers: []string{"192.0.2.0"}}))
+	})
+	It("parses all fields", func() {
+		dns, err := parse(`
+nameserver 192.0.2.0
+nameserver 192.0.2.2
+domain example.com
+;nameserver comment
+#nameserver comment
+search example.net example.org
+search example.gov
+options one two three
+options four
+`)
+		Expect(err).NotTo(HaveOccurred())
+		Expect(*dns).Should(Equal(types.DNS{
+			Nameservers: []string{"192.0.2.0", "192.0.2.2"},
+			Domain:      "example.com",
+			Search:      []string{"example.net", "example.org", "example.gov"},
+			Options:     []string{"one", "two", "three", "four"},
+		}))
+	})
+})
+
+func parse(contents string) (*types.DNS, error) {
+	f, err := ioutil.TempFile("", "host_local_resolv")
+	defer f.Close()
+	defer os.Remove(f.Name())
+
+	if err != nil {
+		return nil, err
+	}
+
+	if _, err := f.WriteString(contents); err != nil {
+		return nil, err
+	}
+
+	return parseResolvConf(f.Name())
+}

plugins/ipam/host-local/host_local_test.go

@@ -38,6 +38,9 @@ var _ = Describe("host-local Operations", func() {
 		Expect(err).NotTo(HaveOccurred())
 		defer os.RemoveAll(tmpDir)
 
+		err = ioutil.WriteFile(filepath.Join(tmpDir, "resolv.conf"), []byte("nameserver 192.0.2.3"), 0644)
+		Expect(err).NotTo(HaveOccurred())
+
 		conf := fmt.Sprintf(`{
     "cniVersion": "0.2.0",
     "name": "mynet",
@@ -46,9 +49,10 @@ var _ = Describe("host-local Operations", func() {
     "ipam": {
         "type": "host-local",
         "subnet": "10.1.2.0/24",
-        "dataDir": "%s"
+        "dataDir": "%s",
+		"resolvConf": "%s/resolv.conf"
     }
-}`, tmpDir)
+}`, tmpDir, tmpDir)
 
 		args := &skel.CmdArgs{
 			ContainerID: "dummy",
@@ -80,6 +84,8 @@ var _ = Describe("host-local Operations", func() {
 		Expect(err).NotTo(HaveOccurred())
 		Expect(string(contents)).To(Equal("10.1.2.2"))
 
+		Expect(result.DNS).To(Equal(types.DNS{Nameservers: []string{"192.0.2.3"}}))
+
 		// Release the IP
 		err = testutils.CmdDelWithResult(nspath, ifname, func() error {
 			return cmdDel(args)

plugins/ipam/host-local/main.go

@@ -33,6 +33,16 @@ func cmdAdd(args *skel.CmdArgs) error {
 		return err
 	}
 
+	r := types.Result{}
+
+	if ipamConf.ResolvConf != "" {
+		dns, err := parseResolvConf(ipamConf.ResolvConf)
+		if err != nil {
+			return err
+		}
+		r.DNS = *dns
+	}
+
 	store, err := disk.New(ipamConf.Name, ipamConf.DataDir)
 	if err != nil {
 		return err
@@ -48,10 +58,8 @@ func cmdAdd(args *skel.CmdArgs) error {
 	if err != nil {
 		return err
 	}
+	r.IP4 = ipConf
 
-	r := &types.Result{
-		IP4: ipConf,
-	}
 	return r.Print()
 }