Merge 3f57b17eb3 into ef45dd3322

util.go

@@ -60,7 +60,13 @@ func GetFirstAndLastIPFromCIDR(cidr string) (firstIP, lastIP net.IP, err error)
 	case net.IPv4len:
 		mask := binary.BigEndian.Uint32(subnet.Mask)
 		ip := binary.BigEndian.Uint32(subnet.IP)
+		// To achieve the first IP address, we need to AND the IP with the mask.
+		// The AND operation will set all bits in the host part to 0.
 		binary.BigEndian.PutUint32(firstIP, ip&mask)
+		// To achieve the last IP address, we need to OR the IP network with the inverted mask.
+		// The AND between the IP and the mask will set all bits in the host part to 0, keeping the network part.
+		// The XOR between the mask and 0xffffffff will set all bits in the host part to 1, and the network part to 0.
+		// The OR operation will keep the host part unchanged, and sets the host part to all 1.
 		binary.BigEndian.PutUint32(lastIP, (ip&mask)|(mask^0xffffffff))
 	case net.IPv6len:
 		mask1 := binary.BigEndian.Uint64(subnet.Mask[:8])