mausezahn: improve random mac address generation

Modify -b option to generate all random MAC addresses.

Improve the random generation algorithm, use nrand48() which fills the
ethernet address in two calls instead of six calls to rand() and six
floating point calculations.

Set the locally administered bit of generated MAC addresses.

Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>

6 files changed, 33 insertions, 47 deletions

diff --git a/mausezahn.8 b/mausezahn.8
index 1ad7667..44a76ab 100644
--- a/mausezahn.8
+++ b/mausezahn.8
@@ -105,18 +105,16 @@ higher layer packets the number of additional padding bytes are specified.
 .PP
 .SS -a <src-mac|keyword>
 Use specified source MAC address with hexadecimal notation such as 00:00:aa:bb:cc:dd.
-By default the interface MAC address will be used. The keywords ''rand'' and
- ''own'' refer to a random MAC address (only unicast addresses are created)
+By default the interface MAC address will be used. The keywords ''rand'' and ''own''
+refer to a random MAC address (only unicast addresses are created)
 and the own address, respectively. You can also use the keywords mentioned
 below although broadcast-type source addresses are officially invalid.
 .PP
 .SS -b <dst-mac|keyword>
 Use specified destination MAC address. By default, a broadcast is sent in raw
 layer 2 mode or to the destination hosts or gateway interface MAC address in normal
-(IP) mode. You can use the same keywords as mentioned above, as well as
- ''bc'' or ''bcast'', ''cisco'', and ''stp''. Please note that for the destination
-MAC address the ''rand'' keyword is supported but creates a random address only
-once, even when you send multiple packets.
+(IP) mode. You can use the same keywords as mentioned above, as well as ''bc''
+or ''bcast'', ''cisco'', and ''stp''.
 .PP
 .SS -A <src-ip|range|rand>
 Use specified source IP address, default is own interface address. Optionally, the
diff --git a/staging/mausezahn.c b/staging/mausezahn.c
index d3d037b..80bfe7d 100644
--- a/staging/mausezahn.c
+++ b/staging/mausezahn.c
@@ -339,6 +339,7 @@ int reset(void)
    // Initialize random generator
    time(&t);
    srand((unsigned int)t);
+   srand48(t);
 
    // Reset device_list
    for (i=0; i<MZ_MAX_DEVICES; i++) {
diff --git a/staging/modifications.c b/staging/modifications.c
index 1affbbb..b105db0 100644
--- a/staging/modifications.c
+++ b/staging/modifications.c
@@ -24,7 +24,7 @@
 //    This sections contains functions to manipulate headers of 
 //    Eth, MPLS, 802.1Q, IP, UDP, and TCP:
 //    
-//      int update_Eth_SA       (libnet_t *l, libnet_ptag_t t)
+//      int rand_addr           (u_int8_t *addr)
 //      int update_IP_SA        (libnet_t *l, libnet_ptag_t t)
 //      int update_IP_DA        (libnet_t *l, libnet_ptag_t t)
 //      int update_IP6_SA       (libnet_t *l, libnet_ptag_t t)
@@ -42,36 +42,19 @@
 #include "mz.h"
 #include "mops.h"
 
-///////////////////////////////////////////////////////////////////////////
-// Applies another random Ethernet source address to a given Ethernet-PTAG.
-// (The calling function should check 'tx.eth_src_rand' whether the SA 
+// Applies another random address to a given buffer.
+// (The calling function should check 'tx.eth_(dst|src)_rand' whether the address
 // should be randomized.)
-// 
-int update_Eth_SA(libnet_t *l, libnet_ptag_t t)
+void rand_addr(u_int8_t *addr)
 {
-   tx.eth_src[0] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256) & 0xFE; // keeps bcast-bit zero
-   tx.eth_src[1] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-   tx.eth_src[2] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-   tx.eth_src[3] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-   tx.eth_src[4] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-   tx.eth_src[5] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
- 
-   t = libnet_build_ethernet (tx.eth_dst, 
-			      tx.eth_src, 
-			      tx.eth_type, 
-			      NULL,              // the payload
-			      0, 
-			      l, 
-			      t);
+   nrand48((unsigned short *)addr);
+   nrand48((unsigned short *)(addr + 3));
 
-   if (t == -1)
-     {
-	fprintf(stderr, " mz/update_Eth_SA: Can't build Ethernet header: %s\n",
-		libnet_geterror(l));
-	exit(EXIT_FAILURE);
-     }
-   
-   return 0;
+   // Get rid of multicast addresses
+   addr[0] &= 0xfe;
+
+   // Set the locally administered bit
+   addr[0] |= 2;
 }
 
 
diff --git a/staging/mz.h b/staging/mz.h
index aa2c36f..6d98ad0 100644
--- a/staging/mz.h
+++ b/staging/mz.h
@@ -726,10 +726,10 @@ int get_mpls_params(char *params);
 int exists(char* str, char* ch);
 
 
-// Applies another random Ethernet source address to a given Ethernet-PTAG.
-// (The calling function should check 'tx.eth_src_rand' whether the SA 
+// Applies another random address to a given buffer.
+// (The calling function should check 'tx.eth_(dst|src)_rand' whether the address
 // should be randomized.)
-int update_Eth_SA(libnet_t *l, libnet_ptag_t t);
+void rand_addr(u_int8_t *addr);
 
 
 // Update timestamp and sequence number in the RTP header.
diff --git a/staging/send_eth.c b/staging/send_eth.c
index ae811e8..b20fb03 100644
--- a/staging/send_eth.c
+++ b/staging/send_eth.c
@@ -55,7 +55,7 @@ libnet_ptag_t  create_eth_frame (libnet_t *l, libnet_ptag_t  t3, libnet_ptag_t
    u_int16_t dot1Q_eth_type=0x8100;
    int bytecnt=0;
 
-   int  isdot1Q, tcp_seq_delta, dp_isrange, sp_isrange, ip_dst_isrange, ip_src_isrange, eth_src_rand, rtp_mode=0;
+   int  isdot1Q, tcp_seq_delta, dp_isrange, sp_isrange, ip_dst_isrange, ip_src_isrange, eth_src_rand, eth_dst_rand, rtp_mode=0;
    unsigned int delay;
 
    
@@ -341,6 +341,7 @@ libnet_ptag_t  create_eth_frame (libnet_t *l, libnet_ptag_t  t3, libnet_ptag_t
    count = tx.count;
    delay = tx.delay;
    eth_src_rand = tx.eth_src_rand;
+   eth_dst_rand = tx.eth_dst_rand;
    tcp_seq_delta = tx.tcp_seq_delta;
    dp_isrange = tx.dp_isrange;
    sp_isrange = tx.sp_isrange;
@@ -374,7 +375,8 @@ libnet_ptag_t  create_eth_frame (libnet_t *l, libnet_ptag_t  t3, libnet_ptag_t
 	     // to libnet_adv_free_packet() should be made to free the memory packet occupies:
 	     libnet_adv_free_packet(l, packet); 
 	     
-	     if (eth_src_rand) update_Eth_SA(L, t);
+	     if (eth_dst_rand) rand_addr(tx.eth_dst);
+	     if (eth_src_rand) rand_addr(tx.eth_src);
 	     
 	     t = libnet_build_ethernet (tx.eth_dst, 
 					tx.eth_src, 
@@ -394,7 +396,15 @@ libnet_ptag_t  create_eth_frame (libnet_t *l, libnet_ptag_t  t3, libnet_ptag_t
 	  }
 	else // No QinQ and/or MPLS modifications => use normal 'l' context:
 	  {
-	     if (eth_src_rand) update_Eth_SA(l, t);
+	     if (eth_dst_rand) rand_addr(tx.eth_dst);
+	     if (eth_src_rand) rand_addr(tx.eth_src);
+	     t = libnet_build_ethernet (tx.eth_dst,
+					tx.eth_src,
+					tx.eth_type,
+					NULL,
+					0,
+					l,
+					t);
 	     if (verbose) (void) print_frame_details();
 	     libnet_write(l);
 	  }
diff --git a/staging/tools.c b/staging/tools.c
index 72445b6..f7c4131 100644
--- a/staging/tools.c
+++ b/staging/tools.c
@@ -687,15 +687,9 @@ int check_eth_mac_txt(int src_or_dst)
    // Okay, lets check the commandline argument:
    // 
    // Do you want a random MAC?
-   // TODO: Consider enforcement of unicast addresses
    if (strncmp(eth_mac_txt, "rand", 4)==0)
      {
-	eth_mac[0] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-	eth_mac[1] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-	eth_mac[2] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-	eth_mac[3] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-	eth_mac[4] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
-	eth_mac[5] = (u_int8_t) ( ((float) rand()/RAND_MAX)*256);
+	rand_addr(eth_mac);
 	*eth_rand = 1;
      }
    // Do you want your own interface MAC?