x/net/icmp: update package documentation
Also fixes typos.
LGTM=iant
R=iant
CC=golang-codereviews
https://golang.org/cl/182410043
diff --git a/icmp/listen_stub.go b/icmp/listen_stub.go
index 1a9be6a..396a556 100644
--- a/icmp/listen_stub.go
+++ b/icmp/listen_stub.go
@@ -12,7 +12,7 @@
// For non-privileged datagram-oriented ICMP endpoints, network must
// be "udp4" or "udp6". The endpoint allows to read, write a few
// limited ICMP messages such as echo request and echo reply.
-// Currently only Dariwn and Linux support this.
+// Currently only Darwin and Linux support this.
//
// Examples:
// ListenPacket("udp4", "192.168.0.1")
diff --git a/icmp/listen_unix.go b/icmp/listen_unix.go
index 5ae9c39..e99e67d 100644
--- a/icmp/listen_unix.go
+++ b/icmp/listen_unix.go
@@ -25,7 +25,7 @@
// For non-privileged datagram-oriented ICMP endpoints, network must
// be "udp4" or "udp6". The endpoint allows to read, write a few
// limited ICMP messages such as echo request and echo reply.
-// Currently only Dariwn and Linux support this.
+// Currently only Darwin and Linux support this.
//
// Examples:
// ListenPacket("udp4", "192.168.0.1")
diff --git a/icmp/message.go b/icmp/message.go
index 2023dbe..3b4f8a4 100644
--- a/icmp/message.go
+++ b/icmp/message.go
@@ -2,8 +2,11 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
-// Package icmp provides basic functions for the manipulation of ICMP
-// message.
+// Package icmp provides basic functions for the manipulation of
+// messages used in the Internet Control Message Protocols,
+// ICMPv4 and ICMPv6.
+//
+// ICMPv4 and ICMPv6 are defined in RFC 792 and RFC 4443.
package icmp
import (
@@ -38,12 +41,12 @@
// Marshal returns the binary enconding of the ICMP message m.
//
-// For ICMP for IPv4 message, the returned message always contains the
+// For an ICMPv4 message, the returned message always contains the
// calculated checksum field.
//
-// For ICMP for IPv6 message, the returned message contains the
-// calculated checksum field when psh is not nil, otherwise the kernel
-// will compute the checksum field during the message transmission.
+// For an ICMPv6 message, the returned message contains the calculated
+// checksum field when psh is not nil, otherwise the kernel will
+// compute the checksum field during the message transmission.
// When psh is not nil, it must be the pseudo header for IPv6.
func (m *Message) Marshal(psh []byte) ([]byte, error) {
var mtype int
