1 files changed, 23 insertions, 19 deletions
diff --git a/dhcpv4/option_router.go b/dhcpv4/option_router.go
index 3154edd..60a96d1 100644
--- a/dhcpv4/option_router.go
+++ b/dhcpv4/option_router.go
@@ -3,6 +3,8 @@ package dhcpv4
 import (
 	"fmt"
 	"net"
+
+	"github.com/u-root/u-root/pkg/uio"
 )
 
 // This option implements the router option
@@ -13,28 +15,30 @@ type OptRouter struct {
 	Routers []net.IP
 }
 
-// ParseOptRouter returns a new OptRouter from a byte stream, or error if any.
-func ParseOptRouter(data []byte) (*OptRouter, error) {
-	if len(data) < 2 {
-		return nil, ErrShortByteStream
-	}
-	code := OptionCode(data[0])
-	if code != OptionRouter {
-		return nil, fmt.Errorf("expected code %v, got %v", OptionRouter, code)
-	}
-	length := int(data[1])
-	if length == 0 || length%4 != 0 {
-		return nil, fmt.Errorf("Invalid length: expected multiple of 4 larger than 4, got %v", length)
+// ParseIPs parses an IPv4 address from a DHCP packet as used and specified by
+// options in RFC 2132, Sections 3.5 through 3.13, 8.2, 8.3, 8.5, 8.6, 8.9, and
+// 8.10.
+func ParseIPs(data []byte) ([]net.IP, error) {
+	buf := uio.NewBigEndianBuffer(data)
+
+	if buf.Len() == 0 {
+		return nil, fmt.Errorf("IP DHCP options must always list at least one IP")
 	}
-	if len(data) < 2+length {
-		return nil, ErrShortByteStream
+
+	ips := make([]net.IP, 0, buf.Len()/net.IPv4len)
+	for buf.Has(net.IPv4len) {
+		ips = append(ips, net.IP(buf.CopyN(net.IPv4len)))
 	}
-	routers := make([]net.IP, 0, length%4)
-	for idx := 0; idx < length; idx += 4 {
-		b := data[2+idx : 2+idx+4]
-		routers = append(routers, net.IPv4(b[0], b[1], b[2], b[3]))
+	return ips, buf.FinError()
+}
+
+// ParseOptRouter returns a new OptRouter from a byte stream, or error if any.
+func ParseOptRouter(data []byte) (*OptRouter, error) {
+	ips, err := ParseIPs(data)
+	if err != nil {
+		return nil, err
 	}
-	return &OptRouter{Routers: routers}, nil
+	return &OptRouter{Routers: ips}, nil
 }
 
 // Code returns the option code.