New option -R to use random bytes instead of NULLs (#72, Anthony DeRobertis)

ChangeLog

@@ -2,6 +2,7 @@ UNRELEASED
   * Use sockaddr_storage and simplify code, so that we can one day
     support both IPv4 and IPv6 with the same binary
   * Fix double entries with fping -u and unreachable hosts
+  * New option -R to use random bytes instead of NULLs (#72, Anthony DeRobertis)
 
 2014-05-03  David Schweikert  <david@schweikert.ch>
   * Version 3.10

doc/fping.pod

@@ -151,6 +151,11 @@ Like B<-q>, but show summary results every n seconds.
 Retry limit (default 3). This is the number of times an attempt at pinging
 a target will be made, not including the first try. 
 
+=item B<-R>
+
+Instead of using all-zeros as the packet data, generate random bytes.
+Use to defeat, e.g., link data compression.
+
 =item B<-s>
 
 Print cumulative statistics upon exit. 

src/Makefile.am

@@ -1,4 +1,4 @@
-AM_CFLAGS = -Wall -Wextra
+AM_CFLAGS = -Wall -Wextra -Wno-sign-compare
 
 prog =
 

src/fping.c

@@ -259,7 +259,6 @@ unsigned int interval = DEFAULT_INTERVAL * 100;
 unsigned int perhost_interval = DEFAULT_PERHOST_INTERVAL * 100;
 float backoff = DEFAULT_BACKOFF_FACTOR;
 unsigned int ping_data_size = DEFAULT_PING_DATA_SIZE;
-unsigned int ping_pkt_size;
 unsigned int count = 1;
 unsigned int trials;
 unsigned int report_interval = 0;
@@ -301,6 +300,7 @@ int elapsed_flag, version_flag, count_flag, loop_flag;
 int per_recv_flag, report_all_rtts_flag, name_flag, addr_flag, backoff_flag;
 int multif_flag;
 int timestamp_flag = 0;
+int random_data_flag = 0;
 #if defined( DEBUG ) || defined( _DEBUG )
 int randomly_lose_flag, sent_times_flag, trace_flag, print_per_system_flag;
 int lose_factor;
@@ -379,7 +379,7 @@ int main( int argc, char **argv )
 
     /* get command line options */
 
-    while( ( c = getopt( argc, argv, "gedhlmnqusaAvDz:t:H:i:p:f:r:c:b:C:Q:B:S:I:T:O:" ) ) != EOF )
+    while( ( c = getopt( argc, argv, "gedhlmnqusaAvDRz:t:H:i:p:f:r:c:b:C:Q:B:S:I:T:O:" ) ) != EOF )
     {
         switch( c )
         {
@@ -475,6 +475,10 @@ int main( int argc, char **argv )
             timestamp_flag = 1;
             break;
 
+        case 'R':
+            random_data_flag = 1;
+            break;
+
         case 'l':
             loop_flag = 1;
             backoff_flag = 0;
@@ -815,8 +819,8 @@ int main( int argc, char **argv )
 
     }/* FOR */
 
-    ping_pkt_size = ping_data_size + SIZE_ICMP_HDR;
+    init_ping_buffer(ping_data_size);
-    
+
     signal( SIGINT, finish );
     
     gettimeofday( &start_time, &tz );
@@ -1407,7 +1411,7 @@ int send_ping( int s, HOST_ENTRY *h )
     n = socket_sendto_ping(s, (struct sockaddr *) &h->saddr, h->saddr_len, myseq, ident);
 
     if(
-        (n < 0 || n != ping_pkt_size)
+        (n < 0)
 #if defined( EHOSTDOWN )
         && errno != EHOSTDOWN
 #endif
@@ -2473,6 +2477,7 @@ void usage(int is_error)
     fprintf(out, "   -q         quiet (don't show per-target/per-ping results)\n" );
     fprintf(out, "   -Q n       same as -q, but show summary every n seconds\n" );
     fprintf(out, "   -r n       number of retries (default %d)\n", DEFAULT_RETRY );
+    fprintf(out, "   -R         random packet data (to foil link data compression)\n" );
     fprintf(out, "   -s         print final stats\n" );
     fprintf(out, "   -S addr    set source address\n" );
     fprintf(out, "   -t n       individual target initial timeout (in millisec) (default %d)\n", timeout / 100 );

src/fping.h

@@ -19,9 +19,11 @@
 void crash_and_burn( char *message );
 void errno_crash_and_burn( char *message );
 int in_cksum( unsigned short *p, int n );
+int random_data_flag;
 
 /* socket.c */
-int  open_ping_socket(size_t ping_data_size);
+int  open_ping_socket();
+void init_ping_buffer(size_t ping_data_size);
 void socket_set_src_addr(int s, FPING_INADDR src_addr);
 int  socket_sendto_ping(int s, struct sockaddr *saddr, socklen_t saddr_len, uint16_t icmp_seq, uint16_t icmp_id);
 

src/socket.c

@@ -35,17 +35,28 @@
 
 int open_ping_socket_ipv4();
 int open_ping_socket_ipv6();
+void init_ping_buffer_ipv4(size_t ping_data_size);
+void init_ping_buffer_ipv6(size_t ping_data_size);
 void socket_set_src_addr_ipv4(int s, FPING_INADDR src_addr);
 void socket_set_src_addr_ipv6(int s, FPING_INADDR src_addr);
 int socket_sendto_ping_ipv4(int s, struct sockaddr *saddr, socklen_t saddr_len, uint16_t icmp_seq_nr, uint16_t icmp_id_nr);
 int socket_sendto_ping_ipv6(int s, struct sockaddr *saddr, socklen_t saddr_len, uint16_t icmp_seq_nr, uint16_t icmp_id_nr);
 
-int open_ping_socket(size_t ping_data_size)
+int open_ping_socket()
 {
 #ifndef IPV6
-    return open_ping_socket_ipv4(ping_data_size);
+    return open_ping_socket_ipv4();
 #else
-    return open_ping_socket_ipv6(ping_data_size);
+    return open_ping_socket_ipv6();
+#endif
+}
+
+void init_ping_buffer(size_t ping_data_size)
+{
+#ifndef IPV6
+    return init_ping_buffer_ipv4(ping_data_size);
+#else
+    return init_ping_buffer_ipv6(ping_data_size);
 #endif
 }
 

src/socket4.c

@@ -45,7 +45,7 @@
 char *ping_buffer = 0;
 size_t ping_pkt_size;
 
-int open_ping_socket_ipv4(size_t ping_data_size)
+int open_ping_socket_ipv4()
 {
     struct protoent *proto;
     int s;
@@ -64,13 +64,16 @@ int open_ping_socket_ipv4(size_t ping_data_size)
         }
     }
 
+    return s;
+}
+
+void init_ping_buffer_ipv4(size_t ping_data_size)
+{
     /* allocate ping buffer */
     ping_pkt_size = ping_data_size + ICMP_MINLEN;
     ping_buffer = (char *) calloc(1, ping_pkt_size);
     if(!ping_buffer)
         crash_and_burn( "can't malloc ping packet" );
-
-    return s;
 }
 
 void socket_set_src_addr_ipv4(int s, FPING_INADDR src_addr)
@@ -93,9 +96,15 @@ int socket_sendto_ping_ipv4(int s, struct sockaddr *saddr, socklen_t saddr_len,
 
     icp->icmp_type = ICMP_ECHO;
     icp->icmp_code = 0;
-    icp->icmp_cksum = 0;
     icp->icmp_seq = htons(icmp_seq_nr);
     icp->icmp_id = htons(icmp_id_nr);
+
+    if (random_data_flag) {
+        for (n = ((void*)&icp->icmp_data - (void *)icp); n < ping_pkt_size; ++n) {
+            ping_buffer[n] = random() & 0xFF;
+        }
+    }
+
     icp->icmp_cksum = in_cksum((unsigned short*) icp, ping_pkt_size );
 
     n = sendto(s, icp, ping_pkt_size, 0, saddr, saddr_len);

src/socket6.c

@@ -45,7 +45,7 @@
 char *ping_buffer = 0;
 size_t ping_pkt_size;
 
-int open_ping_socket_ipv6(size_t ping_data_size)
+int open_ping_socket_ipv6()
 {
     struct protoent *proto;
     int s;
@@ -64,13 +64,16 @@ int open_ping_socket_ipv6(size_t ping_data_size)
         }
     }
 
+    return s;
+}
+
+void init_ping_buffer_ipv6(size_t ping_data_size)
+{
     /* allocate ping buffer */
     ping_pkt_size = ping_data_size + sizeof(struct icmp6_hdr);
     ping_buffer = (char *) calloc(1, ping_pkt_size);
     if(!ping_buffer)
         crash_and_burn( "can't malloc ping packet" );
-
-    return s;
 }
 
 void socket_set_src_addr_ipv6(int s, FPING_INADDR src_addr)
@@ -89,12 +92,18 @@ int socket_sendto_ping_ipv6(int s, struct sockaddr *saddr, socklen_t saddr_len,
     struct icmp6_hdr *icp;
     int n;
 
-    // FIXME: randomization
     icp = (struct icmp6_hdr *) ping_buffer;
     icp->icmp6_type  = ICMP6_ECHO_REQUEST;
     icp->icmp6_code  = 0;
     icp->icmp6_seq   = htons(icmp_seq_nr);
     icp->icmp6_id    = htons(icmp_id_nr);
+
+    if (random_data_flag) {
+        for (n = ((void*)&icp->icmp6_data8 - (void *)icp); n < ping_pkt_size; ++n) {
+            ping_buffer[n] = random() & 0xFF;
+        }
+    }
+
     icp->icmp6_cksum = 0;   // The IPv6 stack calculates the checksum for us...
 
     n = sendto(s, icp, ping_pkt_size, 0, saddr, saddr_len);