nping: Add --badsum option for ICMP mode

This adds support for --badsum flag that already exists and used for
TCP/UDP modes to work for ICMP packets as well.

libnetutil/ICMPv4Header.cc

@@ -453,6 +453,17 @@ int ICMPv4Header::setSum(u16 s){
 } /* End of setSum() */
 
 
+/** Set the ICMP checksum field to a random value that will never
+  * match the correct checksum. This is achieved by computing the correct
+  * checksum first and then XORing it with a random value that can
+  * never be zero. */
+int ICMPv4Header::setSumRandom(){
+  this->setSum();
+  this->h.checksum = this->getSum() ^ (1 + (get_random_u16() % (65535-1)));
+  return OP_SUCCESS;
+} /* End of setSumRandom() */
+
+
 /** Returns the value of the checksum field.
  *  @warning The returned value is in NETWORK byte order, no conversion is
  *  performed */

libnetutil/ICMPv4Header.h

@@ -459,6 +459,7 @@ class ICMPv4Header : public ICMPHeader {
         /* Checksum */
         int setSum();
         int setSum(u16 s);
+        int setSumRandom();
         u16 getSum() const;
 
         /* Unused and reserved fields */

libnetutil/ICMPv6Header.cc

@@ -424,6 +424,14 @@ u16 ICMPv6Header::getSum() const{
 } /* End of getSum() */
 
 
+/** Set the ICMP checksum field to a random value that will never
+  * match the correct checksum */
+int ICMPv6Header::setSumRandom(){
+  this->setSum();
+  this->h.checksum = this->getSum() ^ (1 + (get_random_u16() % (65535-1)));
+  return OP_SUCCESS;
+} /* End of setSumRandom() */
+
 /** @warning Supplied value MUST be in host byte order because it will get
  *  converted by this method using htonl() */
 int ICMPv6Header::setReserved(u32 val){

nping/ArgParser.cc

@@ -135,6 +135,8 @@ int ArgParser::parseArguments(int argc, char *argv[]) {
   {"flags", required_argument, 0, 0},
   {"ack", required_argument, 0, 0},
   {"win", required_argument, 0, 0},
+
+  /* TCP/UDP/ICMP */
   {"badsum", no_argument, 0, 0},
 
   /* ICMP */ 
@@ -1180,6 +1182,7 @@ void ArgParser::printUsage(void){
 "  --icmp-orig-time  <timestamp>    : Set originate timestamp.\n"
 "  --icmp-recv-time  <timestamp>    : Set receive timestamp.\n"
 "  --icmp-trans-time <timestamp>    : Set transmit timestamp.\n"
+"   --badsum                        : Use a random invalid checksum. \n"
 "ARP/RARP PROBE MODE:\n"
 "  --arp-type <type>                : Type: ARP, ARP-reply, RARP, RARP-reply.\n"
 "  --arp-sender-mac <mac>           : Set sender MAC address.\n"

nping/NpingOps.cc

@@ -225,9 +225,6 @@ NpingOps::NpingOps() {
     icmp_code=0;
     icmp_code_set=false;
 
-    badsum_icmp=false;
-    badsum_icmp_set=false;
-
     icmp_redir_addr.s_addr=0;
     icmp_redir_addr_set=false;
 
@@ -1672,40 +1669,6 @@ bool NpingOps::issetICMPCode(){
 } /* End of issetICMPCode() */
 
 
-/** Sets attribute badsum_icmp to "true". (Generate invalid checksums in ICMP
- *  packets)
- *  @return previous value of the attribute. */
-bool NpingOps::enableBadsumICMP() {
-  bool prev = this->badsum_icmp;
-  this->badsum_icmp=true;
-  this->badsum_icmp_set=true;
-  return prev;
-} /* End of enableBadsumICMPTCP() */
-
-
-/** Sets attribute traceroute to "false". (Do NOT Generate invalid checksums
- *  in UDP / TCP packets)
- *  @return previous value of the attribute. */
-bool NpingOps::disableBadsumICMP() {
-  bool prev = this->badsum_icmp;
-  this->badsum_icmp=false;
-  this->badsum_icmp_set=true;
-  return prev;
-} /* End of disableBadsumICMP() */
-
-
-/** Returns value of attribute badsum_icmp */
-bool NpingOps::getBadsumICMP() {
-  return this->badsum_icmp;
-} /* End of getBadsumICMP() */
-
-
-/* Returns true if option has been set */
-bool NpingOps::issetBadsumICMP(){
-  return this->badsum_icmp_set;
-} /* End of issetBadsumICMP() */
-
-
 /** Sets ICMPRedirectAddress.
  *  @return OP_SUCCESS on success and OP_FAILURE in case of error.           */
 int NpingOps::setICMPRedirectAddress(struct in_addr val){

nping/NpingOps.h

@@ -210,7 +210,7 @@ class NpingOps {
     bool tcpflags_set;
     u16 tcpwin;               /* TCP Window                            */
     bool tcpwin_set;
-    bool badsum;              /* Generate invalid TCP/UDP checksums?   */
+    bool badsum;              /* Generate invalid TCP/UDP/ICMP checksums? */
     bool badsum_set;
 
     /* ICMP */
@@ -218,8 +218,6 @@ class NpingOps {
     bool icmp_type_set;
     u8 icmp_code;             /* ICMP Code                             */
     bool icmp_code_set;
-    bool badsum_icmp;         /* Generate invalid ICMP checksums?      */
-    bool badsum_icmp_set;
     struct in_addr icmp_redir_addr; /* ICMP Redirect Address */ /* ##TODO## Turn this into an IPAddress object */
     bool icmp_redir_addr_set;
     u8 icmp_paramprob_pnt;    /* ICMP Parameter Problem pointer        */

nping/ProbeMode.cc

@@ -1082,7 +1082,10 @@ int ProbeMode::fillPacketICMP(NpingTarget *target, u8 *buff, int bufflen, int *f
 
     }
     /* Compute checksum */
-    c4.setSum(); /* TODO: Do we want to implement --badsum-icmp? */
+    if( o.getBadsum() == true )
+      c4.setSumRandom();
+    else
+      c4.setSum();
 
     /* Fill the IPv4Header object with the info from NpingOps */
     createIPv4(&i, &c4, "ICMP", target);
@@ -1122,7 +1125,10 @@ int ProbeMode::fillPacketICMP(NpingTarget *target, u8 *buff, int bufflen, int *f
     createIPv6(&i6, &c6, "ICMPv6", target);
 
     /* Compute checksum */
-    c6.setSum();
+    if( o.getBadsum() == true )
+      c6.setSumRandom();
+    else
+      c6.setSum();
 
     /* Store result in user supplied buffer */
     *filledlen = i6.dumpToBinaryBuffer(buff, bufflen);