vendor: update all dependencies

* Update all dependencies
  * Remove all `[[constraint]]` from Gopkg.toml
  * Add in the minimum number of `[[override]]` to build
  * Remove go get of github.com/inconshreveable/mousetrap as it is vendored
  * Update docs with new policy on constraints

vendor/golang.org/x/net/icmp/extension.go

@@ -4,7 +4,12 @@
 
 package icmp
 
-import "encoding/binary"
+import (
+	"encoding/binary"
+
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
+)
 
 // An Extension represents an ICMP extension.
 type Extension interface {
@@ -38,7 +43,7 @@ func validExtensionHeader(b []byte) bool {
 // It will return a list of ICMP extensions and an adjusted length
 // attribute that represents the length of the padded original
 // datagram field. Otherwise, it returns an error.
-func parseExtensions(b []byte, l int) ([]Extension, int, error) {
+func parseExtensions(typ Type, b []byte, l int) ([]Extension, int, error) {
 	// Still a lot of non-RFC 4884 compliant implementations are
 	// out there. Set the length attribute l to 128 when it looks
 	// inappropriate for backwards compatibility.
@@ -48,20 +53,28 @@ func parseExtensions(b []byte, l int) ([]Extension, int, error) {
 	// header.
 	//
 	// See RFC 4884 for further information.
-	if 128 > l || l+8 > len(b) {
-		l = 128
-	}
-	if l+8 > len(b) {
-		return nil, -1, errNoExtension
-	}
-	if !validExtensionHeader(b[l:]) {
-		if l == 128 {
+	switch typ {
+	case ipv4.ICMPTypeExtendedEchoRequest, ipv6.ICMPTypeExtendedEchoRequest:
+		if len(b) < 8 || !validExtensionHeader(b) {
 			return nil, -1, errNoExtension
 		}
-		l = 128
-		if !validExtensionHeader(b[l:]) {
+		l = 0
+	default:
+		if 128 > l || l+8 > len(b) {
+			l = 128
+		}
+		if l+8 > len(b) {
 			return nil, -1, errNoExtension
 		}
+		if !validExtensionHeader(b[l:]) {
+			if l == 128 {
+				return nil, -1, errNoExtension
+			}
+			l = 128
+			if !validExtensionHeader(b[l:]) {
+				return nil, -1, errNoExtension
+			}
+		}
 	}
 	var exts []Extension
 	for b = b[l+4:]; len(b) >= 4; {
@@ -82,6 +95,12 @@ func parseExtensions(b []byte, l int) ([]Extension, int, error) {
 				return nil, -1, err
 			}
 			exts = append(exts, ext)
+		case classInterfaceIdent:
+			ext, err := parseInterfaceIdent(b[:ol])
+			if err != nil {
+				return nil, -1, err
+			}
+			exts = append(exts, ext)
 		}
 		b = b[ol:]
 	}