fix checksum bug

1 files changed, 17 insertions, 5 deletions

diff --git a/pkg/ipstack/ipstack.go b/pkg/ipstack/ipstack.go
index 334aab5..4a552cf 100644
--- a/pkg/ipstack/ipstack.go
+++ b/pkg/ipstack/ipstack.go
@@ -402,7 +402,21 @@ func SendIP(src *netip.Addr, dest *Neighbor, protocolNum int, message []byte, de
 			Options:  []byte{},
 		}
 	} else {
-		hdr.TTL--
+		hdr = &ipv4header.IPv4Header{
+			Version:  4,
+			Len:      20, // Header length is always 20 when no IP options
+			TOS:      0,
+			TotalLen: ipv4header.HeaderLen + len(message),
+			ID:       0,
+			Flags:    0,
+			FragOff:  0,
+			TTL:      hdr.TTL - 1,
+			Protocol: protocolNum,
+			Checksum: 0, // Should be 0 until checksum is computed
+			Src:      *src,
+			Dst:      netip.MustParseAddr(destIP),
+			Options:  []byte{},
+		}
 	}
 
 	// Assemble the header into a byte array
@@ -442,8 +456,6 @@ func SendIP(src *netip.Addr, dest *Neighbor, protocolNum int, message []byte, de
 }
 
 func RecvIP(iface *Interface, isOpen *bool) error {
-	fmt.Printf("Receiving IP packet on %s\n", iface.Name)
-
 	// deconstruct interface
 	prefix := iface.IpPrefix
 	conn := iface.RecvSocket
@@ -541,7 +553,7 @@ func RecvIP(iface *Interface, isOpen *bool) error {
 			// if it's a local route, then the name is the interface name
 			for _, neighbor := range myNeighbors[hop.Interface.Name] {
 				if neighbor.VipAddr == hdr.Dst {
-					err2 := SendIP(nil, neighbor, hdr.Protocol, message, hdr.Dst.String(), hdr)
+					err2 := SendIP(&hdr.Src, neighbor, hdr.Protocol, message, hdr.Dst.String(), hdr)
 					if err2 != nil {
 						return err2
 					}
@@ -554,7 +566,7 @@ func RecvIP(iface *Interface, isOpen *bool) error {
 			// if it's a rip route, then the check is against the hop vip
 			for _, neighbor := range myNeighbors[hop.Interface.Name] {
 				if neighbor.VipAddr == hop.VIP {
-					err2 := SendIP(nil, neighbor, hdr.Protocol, message, hdr.Dst.String(), hdr)
+					err2 := SendIP(&hdr.Src, neighbor, hdr.Protocol, message, hdr.Dst.String(), hdr)
 					if err2 != nil {
 						return err2
 					}