RPC and HTTP interfaces fully generically-sockified so Unix is supported.

Client works for RPC; will honor CONSUL_RPC_ADDR. HTTP works via consul/api;
honors CONSUL_HTTP_ADDR.

The format of a Unix socket in configuration data is:
"unix://[/path/to/socket];[username or uid];[gid];[mode]"

Obviously, the user must have appropriate permissions to create the socket
file in the given path and assign the requested uid/gid. Also note that Go does
not support gid lookups from group name, so gid must be numeric. See
https://codereview.appspot.com/101310044

When connecting from the client, the format is just the first part of the
above line:
"unix://[/path/to/socket]"

This code is copyright 2014 Akamai Technologies, Inc. <opensource@akamai.com>

api/api.go

@@ -5,9 +5,12 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"net/url"
+	"os"
 	"strconv"
+	"strings"
 	"time"
 )
 
@@ -111,11 +114,17 @@ type Config struct {
 
 // DefaultConfig returns a default configuration for the client
 func DefaultConfig() *Config {
-	return &Config{
+	config := &Config{
 		Address:    "127.0.0.1:8500",
 		Scheme:     "http",
 		HttpClient: http.DefaultClient,
 	}
+
+	if len(os.Getenv("CONSUL_HTTP_ADDR")) > 0 {
+		config.Address = os.Getenv("CONSUL_HTTP_ADDR")
+	}
+
+	return config
 }
 
 // Client provides a client to the Consul API
@@ -128,7 +137,11 @@ func NewClient(config *Config) (*Client, error) {
 	// bootstrap the config
 	defConfig := DefaultConfig()
 
-	if len(config.Address) == 0 {
+	switch {
+	case len(config.Address) != 0:
+	case len(os.Getenv("CONSUL_HTTP_ADDR")) > 0:
+		config.Address = os.Getenv("CONSUL_HTTP_ADDR")
+	default:
 		config.Address = defConfig.Address
 	}
 
@@ -140,6 +153,16 @@ func NewClient(config *Config) (*Client, error) {
 		config.HttpClient = defConfig.HttpClient
 	}
 
+	if strings.HasPrefix(config.Address, "unix://") {
+		shortStr := strings.TrimPrefix(config.Address, "unix://")
+		t := &http.Transport{}
+		t.Dial = func(_, _ string) (net.Conn, error) {
+			return net.Dial("unix", shortStr)
+		}
+		config.HttpClient.Transport = t
+		config.Address = shortStr
+	}
+
 	client := &Client{
 		config: *config,
 	}
@@ -206,9 +229,6 @@ func (r *request) toHTTP() (*http.Request, error) {
 	// Encode the query parameters
 	r.url.RawQuery = r.params.Encode()
 
-	// Get the url sring
-	urlRaw := r.url.String()
-
 	// Check if we should encode the body
 	if r.body == nil && r.obj != nil {
 		if b, err := encodeBody(r.obj); err != nil {
@@ -219,14 +239,21 @@ func (r *request) toHTTP() (*http.Request, error) {
 	}
 
 	// Create the HTTP request
-	req, err := http.NewRequest(r.method, urlRaw, r.body)
+	req, err := http.NewRequest(r.method, r.url.RequestURI(), r.body)
+	if err != nil {
+		return nil, err
+	}
+
+	req.URL.Host = r.url.Host
+	req.URL.Scheme = r.url.Scheme
+	req.Host = r.url.Host
 
 	// Setup auth
 	if err == nil && r.config.HttpAuth != nil {
 		req.SetBasicAuth(r.config.HttpAuth.Username, r.config.HttpAuth.Password)
 	}
 
-	return req, err
+	return req, nil
 }
 
 // newRequest is used to create a new request

command/agent/command.go

@@ -295,13 +295,26 @@ func (c *Command) setupAgent(config *Config, logOutput io.Writer, logWriter *log
 		return err
 	}
 
-	rpcListener, err := net.Listen("tcp", rpcAddr.String())
+	if _, ok := rpcAddr.(*net.UnixAddr); ok {
+		// Remove the socket if it exists, or we'll get a bind error
+		_ = os.Remove(rpcAddr.String())
+	}
+
+	rpcListener, err := net.Listen(rpcAddr.Network(), rpcAddr.String())
 	if err != nil {
 		agent.Shutdown()
 		c.Ui.Error(fmt.Sprintf("Error starting RPC listener: %s", err))
 		return err
 	}
 
+	if _, ok := rpcAddr.(*net.UnixAddr); ok {
+		if err := adjustUnixSocketPermissions(config.Addresses.RPC); err != nil {
+			agent.Shutdown()
+			c.Ui.Error(fmt.Sprintf("Error adjusting Unix socket permissions: %s", err))
+			return err
+		}
+	}
+
 	// Start the IPC layer
 	c.Ui.Output("Starting Consul agent RPC...")
 	c.rpcServer = NewAgentRPC(agent, rpcListener, logOutput, logWriter)
@@ -319,6 +332,7 @@ func (c *Command) setupAgent(config *Config, logOutput io.Writer, logWriter *log
 	if config.Ports.DNS > 0 {
 		dnsAddr, err := config.ClientListener(config.Addresses.DNS, config.Ports.DNS)
 		if err != nil {
+			agent.Shutdown()
 			c.Ui.Error(fmt.Sprintf("Invalid DNS bind address: %s", err))
 			return err
 		}

command/agent/config.go

@@ -7,8 +7,10 @@ import (
 	"io"
 	"net"
 	"os"
+	"os/user"
 	"path/filepath"
 	"sort"
+	"strconv"
 	"strings"
 	"time"
 
@@ -345,6 +347,82 @@ type Config struct {
 	WatchPlans []*watch.WatchPlan `mapstructure:"-" json:"-"`
 }
 
+// UnixSocket contains the parameters for a Unix socket interface
+type UnixSocket struct {
+	// Path to the socket on-disk
+	Path string
+
+	// uid of the owner of the socket
+	Uid int
+
+	// gid of the group of the socket
+	Gid int
+
+	// Permissions for the socket file
+	Permissions os.FileMode
+}
+
+func populateUnixSocket(addr string) (*UnixSocket, error) {
+	if !strings.HasPrefix(addr, "unix://") {
+		return nil, fmt.Errorf("Failed to parse Unix address, format is [path];[user];[group];[mode]: %v", addr)
+	}
+
+	splitAddr := strings.Split(strings.TrimPrefix(addr, "unix://"), ";")
+	if len(splitAddr) != 4 {
+		return nil, fmt.Errorf("Failed to parse Unix address, format is [path];[user];[group];[mode]: %v", addr)
+	}
+
+	ret := &UnixSocket{Path: splitAddr[0]}
+
+	if userVal, err := user.Lookup(splitAddr[1]); err != nil {
+		return nil, fmt.Errorf("Invalid user given for Unix socket ownership: %v", splitAddr[1])
+	} else {
+		if uid64, err := strconv.ParseInt(userVal.Uid, 10, 32); err != nil {
+			return nil, fmt.Errorf("Failed to parse given user ID of %v into integer", userVal.Uid)
+		} else {
+			ret.Uid = int(uid64)
+		}
+	}
+
+	// Go doesn't currently have a way to look up gid from group name,
+	// so require a numeric gid; see
+	// https://codereview.appspot.com/101310044
+	if gid64, err := strconv.ParseInt(splitAddr[2], 10, 32); err != nil {
+		return nil, fmt.Errorf("Socket group must be given as numeric gid. Failed to parse given group ID of %v into integer", splitAddr[2])
+	} else {
+		ret.Gid = int(gid64)
+	}
+
+	if mode, err := strconv.ParseUint(splitAddr[3], 8, 32); err != nil {
+		return nil, fmt.Errorf("Failed to parse given mode of %v into integer", splitAddr[3])
+	} else {
+		if mode > 0777 {
+			return nil, fmt.Errorf("Given mode is invalid; must be an octal number between 0 and 777")
+		} else {
+			ret.Permissions = os.FileMode(mode)
+		}
+	}
+
+	return ret, nil
+}
+
+func adjustUnixSocketPermissions(addr string) error {
+	sock, err := populateUnixSocket(addr)
+	if err != nil {
+		return err
+	}
+
+	if err = os.Chown(sock.Path, sock.Uid, sock.Gid); err != nil {
+		return fmt.Errorf("Error attempting to change socket permissions to userid %v and groupid %v: %v", sock.Uid, sock.Gid, err)
+	}
+
+	if err = os.Chmod(sock.Path, sock.Permissions); err != nil {
+		return fmt.Errorf("Error attempting to change socket permissions to mode %v: %v", sock.Permissions, err)
+	}
+
+	return nil
+}
+
 type dirEnts []os.FileInfo
 
 // DefaultConfig is used to return a sane default configuration
@@ -389,18 +467,30 @@ func (c *Config) EncryptBytes() ([]byte, error) {
 
 // ClientListener is used to format a listener for a
 // port on a ClientAddr
-func (c *Config) ClientListener(override string, port int) (*net.TCPAddr, error) {
+func (c *Config) ClientListener(override string, port int) (net.Addr, error) {
 	var addr string
 	if override != "" {
 		addr = override
 	} else {
 		addr = c.ClientAddr
 	}
+
+	switch {
+	case strings.HasPrefix(addr, "unix://"):
+		sock, err := populateUnixSocket(addr)
+		if err != nil {
+			return nil, err
+		}
+
+		return &net.UnixAddr{Name: sock.Path, Net: "unix"}, nil
+
+	default:
 		ip := net.ParseIP(addr)
 		if ip == nil {
 			return nil, fmt.Errorf("Failed to parse IP: %v", addr)
 		}
 		return &net.TCPAddr{IP: ip, Port: port}, nil
+	}
 }
 
 // ClientListenerAddr is used to format an address for a
@@ -410,8 +500,11 @@ func (c *Config) ClientListenerAddr(override string, port int) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	if addr.IP.IsUnspecified() {
-		addr.IP = net.ParseIP("127.0.0.1")
+
+	if ipAddr, ok := addr.(*net.TCPAddr); ok {
+		if ipAddr.IP.IsUnspecified() {
+			ipAddr.IP = net.ParseIP("127.0.0.1")
+		}
 	}
 	return addr.String(), nil
 }

command/agent/http.go

@@ -9,6 +9,7 @@ import (
 	"net"
 	"net/http"
 	"net/http/pprof"
+	"os"
 	"strconv"
 	"strings"
 	"time"
@@ -34,7 +35,7 @@ type HTTPServer struct {
 func NewHTTPServers(agent *Agent, config *Config, logOutput io.Writer) ([]*HTTPServer, error) {
 	var tlsConfig *tls.Config
 	var list net.Listener
-	var httpAddr *net.TCPAddr
+	var httpAddr net.Addr
 	var err error
 	var servers []*HTTPServer
 
@@ -58,13 +59,30 @@ func NewHTTPServers(agent *Agent, config *Config, logOutput io.Writer) ([]*HTTPS
 			return nil, err
 		}
 
-		ln, err := net.Listen("tcp", httpAddr.String())
-		if err != nil {
-			return nil, err
+		if _, ok := httpAddr.(*net.UnixAddr); ok {
+			// Remove the socket if it exists, or we'll get a bind error
+			_ = os.Remove(httpAddr.String())
 		}
 
+		ln, err := net.Listen(httpAddr.Network(), httpAddr.String())
+		if err != nil {
+			return nil, fmt.Errorf("Failed to get Listen on %s: %v", httpAddr.String(), err)
+		}
+
+		switch httpAddr.(type) {
+		case *net.UnixAddr:
+			if err := adjustUnixSocketPermissions(config.Addresses.HTTPS); err != nil {
+				return nil, err
+			}
+			list = tls.NewListener(ln, tlsConfig)
+
+		case *net.TCPAddr:
 			list = tls.NewListener(tcpKeepAliveListener{ln.(*net.TCPListener)}, tlsConfig)
 
+		default:
+			return nil, fmt.Errorf("Error determining address type when attempting to get Listen on %s: %v", httpAddr.String(), err)
+		}
+
 		// Create the mux
 		mux := http.NewServeMux()
 
@@ -90,14 +108,30 @@ func NewHTTPServers(agent *Agent, config *Config, logOutput io.Writer) ([]*HTTPS
 			return nil, fmt.Errorf("Failed to get ClientListener address:port: %v", err)
 		}
 
-		// Create non-TLS listener
-		ln, err := net.Listen("tcp", httpAddr.String())
+		if _, ok := httpAddr.(*net.UnixAddr); ok {
+			// Remove the socket if it exists, or we'll get a bind error
+			_ = os.Remove(httpAddr.String())
+		}
+
+		ln, err := net.Listen(httpAddr.Network(), httpAddr.String())
 		if err != nil {
 			return nil, fmt.Errorf("Failed to get Listen on %s: %v", httpAddr.String(), err)
 		}
 
+		switch httpAddr.(type) {
+		case *net.UnixAddr:
+			if err := adjustUnixSocketPermissions(config.Addresses.HTTP); err != nil {
+				return nil, err
+			}
+			list = ln
+
+		case *net.TCPAddr:
 			list = tcpKeepAliveListener{ln.(*net.TCPListener)}
 
+		default:
+			return nil, fmt.Errorf("Error determining address type when attempting to get Listen on %s: %v", httpAddr.String(), err)
+		}
+
 		// Create the mux
 		mux := http.NewServeMux()
 

command/agent/rpc_client.go

@@ -7,6 +7,8 @@ import (
 	"github.com/hashicorp/logutils"
 	"log"
 	"net"
+	"os"
+	"strings"
 	"sync"
 	"sync/atomic"
 )
@@ -34,7 +36,7 @@ type seqHandler interface {
 type RPCClient struct {
 	seq uint64
 
-	conn      *net.TCPConn
+	conn      net.Conn
 	reader    *bufio.Reader
 	writer    *bufio.Writer
 	dec       *codec.Decoder
@@ -79,8 +81,18 @@ func (c *RPCClient) send(header *requestHeader, obj interface{}) error {
 // NewRPCClient is used to create a new RPC client given the address.
 // This will properly dial, handshake, and start listening
 func NewRPCClient(addr string) (*RPCClient, error) {
+	sanedAddr := os.Getenv("CONSUL_RPC_ADDR")
+	if len(sanedAddr) == 0 {
+		sanedAddr = addr
+	}
+	mode := "tcp"
+	if strings.HasPrefix(sanedAddr, "unix://") {
+		sanedAddr = strings.TrimPrefix(sanedAddr, "unix://")
+		mode = "unix"
+	}
+
 	// Try to dial to agent
-	conn, err := net.Dial("tcp", addr)
+	conn, err := net.Dial(mode, sanedAddr)
 	if err != nil {
 		return nil, err
 	}
@@ -88,7 +100,7 @@ func NewRPCClient(addr string) (*RPCClient, error) {
 	// Create the client
 	client := &RPCClient{
 		seq:        0,
-		conn:       conn.(*net.TCPConn),
+		conn:       conn,
 		reader:     bufio.NewReader(conn),
 		writer:     bufio.NewWriter(conn),
 		dispatch:   make(map[uint64]seqHandler),

command/rpc.go

@@ -8,8 +8,8 @@ import (
 	"github.com/hashicorp/consul/command/agent"
 )
 
-// RPCAddrEnvName defines the environment variable name, which can set
-// a default RPC address in case there is no -rpc-addr specified.
+// RPCAddrEnvName defines an environment variable name which sets
+// an RPC address if there is no -rpc-addr specified.
 const RPCAddrEnvName = "CONSUL_RPC_ADDR"
 
 // RPCAddrFlag returns a pointer to a string that will be populated
@@ -43,7 +43,12 @@ func HTTPClient(addr string) (*consulapi.Client, error) {
 // HTTPClientDC returns a new Consul HTTP client with the given address and datacenter
 func HTTPClientDC(addr, dc string) (*consulapi.Client, error) {
 	conf := consulapi.DefaultConfig()
+	switch {
+	case len(os.Getenv("CONSUL_HTTP_ADDR")) > 0:
+		conf.Address = os.Getenv("CONSUL_HTTP_ADDR")
+	default:
 		conf.Address = addr
+	}
 	conf.Datacenter = dc
 	return consulapi.NewClient(conf)
 }