net: implement network interface API for Plan 9

The new implementation parses the plan9 interface files
and builds Interface representations for the net package.

Updates #17218

Change-Id: I3199d18d9e96a17e922186c3abff1d7cd9cbec2e
Reviewed-on: https://go-review.googlesource.com/29963
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/interface.go

@@ -10,7 +10,7 @@ import (
 	"time"
 )
 
-// BUG(mikio): On NaCl and Plan9, methods and functions related to
+// BUG(mikio): On NaCl, methods and functions related to
 // Interface are not implemented.
 
 // BUG(mikio): On DragonFly BSD, NetBSD, OpenBSD and Solaris, the

src/net/interface_plan9.go

+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package net
+
+import (
+	"errors"
+	"os"
+)
+
+// If the ifindex is zero, interfaceTable returns mappings of all
+// network interfaces. Otherwise it returns a mapping of a specific
+// interface.
+func interfaceTable(ifindex int) ([]Interface, error) {
+	if ifindex == 0 {
+		n, err := interfaceCount()
+		if err != nil {
+			return nil, err
+		}
+		ifcs := make([]Interface, n)
+		for i := range ifcs {
+			ifc, err := readInterface(i)
+			if err != nil {
+				return nil, err
+			}
+			ifcs[i] = *ifc
+		}
+		return ifcs, nil
+	}
+
+	ifc, err := readInterface(ifindex - 1)
+	if err != nil {
+		return nil, err
+	}
+	return []Interface{*ifc}, nil
+}
+
+func readInterface(i int) (*Interface, error) {
+	ifc := &Interface{
+		Index: i + 1,                        // Offset the index by one to suit the contract
+		Name:  netdir + "/ipifc/" + itoa(i), // Name is the full path to the interface path in plan9
+	}
+
+	ifcstat := ifc.Name + "/status"
+	ifcstatf, err := open(ifcstat)
+	if err != nil {
+		return nil, err
+	}
+	defer ifcstatf.close()
+
+	line, ok := ifcstatf.readLine()
+	if !ok {
+		return nil, errors.New("invalid interface status file: " + ifcstat)
+	}
+
+	fields := getFields(line)
+	if len(fields) < 4 {
+		return nil, errors.New("invalid interface status file: " + ifcstat)
+	}
+
+	device := fields[1]
+	mtustr := fields[3]
+
+	mtu, _, ok := dtoi(mtustr)
+	if !ok {
+		return nil, errors.New("invalid status file of interface: " + ifcstat)
+	}
+	ifc.MTU = mtu
+
+	// Not a loopback device
+	if device != "/dev/null" {
+		deviceaddrf, err := open(device + "/addr")
+		if err != nil {
+			return nil, err
+		}
+		defer deviceaddrf.close()
+
+		line, ok = deviceaddrf.readLine()
+		if !ok {
+			return nil, errors.New("invalid address file for interface: " + device + "/addr")
+		}
+
+		if len(line) > 0 && len(line)%2 == 0 {
+			ifc.HardwareAddr = make([]byte, len(line)/2)
+			var ok bool
+			for i := range ifc.HardwareAddr {
+				j := (i + 1) * 2
+				ifc.HardwareAddr[i], ok = xtoi2(line[i*2:j], 0)
+				if !ok {
+					ifc.HardwareAddr = ifc.HardwareAddr[:i]
+					break
+				}
+			}
+		}
+
+		ifc.Flags = FlagUp | FlagBroadcast | FlagMulticast
+	} else {
+		ifc.Flags = FlagUp | FlagMulticast | FlagLoopback
+	}
+
+	return ifc, nil
+}
+
+func interfaceCount() (int, error) {
+	d, err := os.Open(netdir + "/ipifc")
+	if err != nil {
+		return -1, err
+	}
+	defer d.Close()
+
+	names, err := d.Readdirnames(0)
+	if err != nil {
+		return -1, err
+	}
+
+	// Assumes that numbered files in ipifc are strictly
+	// the incrementing numbered directories for the
+	// interfaces
+	c := 0
+	for _, name := range names {
+		if _, _, ok := dtoi(name); !ok {
+			continue
+		}
+		c++
+	}
+
+	return c, nil
+}
+
+// If the ifi is nil, interfaceAddrTable returns addresses for all
+// network interfaces. Otherwise it returns addresses for a specific
+// interface.
+func interfaceAddrTable(ifi *Interface) ([]Addr, error) {
+	ifcs := []Interface{}
+	if ifi == nil {
+		var err error
+		ifcs, err = interfaceTable(0)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		ifcs = []Interface{*ifi}
+	}
+
+	addrs := make([]Addr, len(ifcs))
+	for i, ifc := range ifcs {
+		status := ifc.Name + "/status"
+		statusf, err := open(status)
+		if err != nil {
+			return nil, err
+		}
+		defer statusf.close()
+
+		line, ok := statusf.readLine()
+		line, ok = statusf.readLine()
+		if !ok {
+			return nil, errors.New("cannot parse IP address for interface: " + status)
+		}
+
+		// This assumes only a single address for the interface.
+		fields := getFields(line)
+		if len(fields) < 1 {
+			return nil, errors.New("cannot parse IP address for interface: " + status)
+		}
+		addr := fields[0]
+		ip := ParseIP(addr)
+		if ip == nil {
+			return nil, errors.New("cannot parse IP address for interface: " + status)
+		}
+
+		// The mask is represented as CIDR relative to the IPv6 address.
+		// Plan 9 internal representation is always IPv6.
+		maskfld := fields[1]
+		maskfld = maskfld[1:]
+		pfxlen, _, ok := dtoi(maskfld)
+		if !ok {
+			return nil, errors.New("cannot parse network mask for interface: " + status)
+		}
+		mask := CIDRMask(int(pfxlen), 128)
+
+		if ip.To4() != nil { // IPv4 or IPv6 IPv4-mapped address
+			mask = CIDRMask(pfxlen-8*len(v4InV6Prefix), 8*IPv4len)
+		}
+		if ip.To16() != nil && ip.To4() == nil { // IPv6 address
+			mask = CIDRMask(pfxlen, 8*IPv6len)
+		}
+
+		addrs[i] = &IPNet{IP: ip, Mask: mask}
+	}
+
+	return addrs, nil
+}
+
+// interfaceMulticastAddrTable returns addresses for a specific
+// interface.
+func interfaceMulticastAddrTable(ifi *Interface) ([]Addr, error) {
+	return nil, nil
+}

src/net/interface_stub.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build nacl plan9
+// +build nacl
 
 package net