From 48a8b2f6a64d8899fe048af62782cee5230bad27 Mon Sep 17 00:00:00 2001
From: "Alexander V. Barsamian" <abarsam@Cardinal.local>
Date: Thu, 7 Sep 2017 08:09:34 -1000
Subject: [PATCH] support for specifying spoofed IP

---
 read_config.c | 38 +++++++++++++++++++++++++++++++++-----
 samplicate.c  | 12 +++++++++++-
 samplicator.h |  8 ++++++++
 3 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/read_config.c b/read_config.c
index a3449d9..70f3531 100644
--- a/read_config.c
+++ b/read_config.c
@@ -493,8 +493,28 @@ parse_receiver (struct receiver *receiverp,
   char portspec[NI_MAXSERV];
   struct addrinfo hints, *res;
   int result;
-
+  
   receiverp->flags = ctx->default_receiver_flags;
+
+  if(receiverp->flags & pf_SPOOF_WITH_IP) {
+
+    init_hints_from_preferences (&hints, ctx);
+    {
+      result = getaddrinfo (ctx->spoofed_src_addr, NULL, &hints, &res);
+
+      if (result != 0)
+        {
+  	return parse_error (ctx, "Parsing IP address (%s) failed", ctx->spoofed_src_addr);
+        }
+        
+      memcpy (&(receiverp->spoofed_src_addr), res->ai_addr, res->ai_addrlen);
+      receiverp->spoofed_src_addrlen = res->ai_addrlen;
+      freeaddrinfo(res);
+    }
+    
+      
+  }
+    
   receiverp->freqcount = 0;
   receiverp->freq = 1;
   receiverp->ttl = DEFAULT_TTL; 
@@ -768,6 +788,9 @@ parse_args (argc, argv, ctx)
   ctx->pid_file = (const char *) 0;
   ctx->sources = 0;
   ctx->default_receiver_flags = pf_CHECKSUM;
+  
+  ctx->spoofed_src_addr = NULL;
+  
   /* assume that command-line supplied receivers want to get all data */
   sctx->source.ss_family = AF_INET;
   ((struct sockaddr_in *) &sctx->source)->sin_addr.s_addr = 0;
@@ -776,7 +799,7 @@ parse_args (argc, argv, ctx)
   sctx->tx_delay = 0;
 
   optind = 1;
-  while ((i = getopt (argc, (char **) argv, "hu:b:d:t:m:p:s:x:c:fSn46")) != -1)
+  while ((i = getopt (argc, (char **) argv, "P:hu:b:d:t:m:p:s:x:c:fSn46")) != -1)
     {
       switch (i)
 	{
@@ -807,9 +830,13 @@ parse_args (argc, argv, ctx)
 	case 'x': /* transmit delay */
 	  sctx->tx_delay = atoi (optarg);
 	  break;
+  case 'P':
+    ctx->default_receiver_flags |= pf_SPOOF_WITH_IP;
+    ctx->spoofed_src_addr = optarg;
+    break;
 	case 'S': /* spoof */
-	  ctx->default_receiver_flags |= pf_SPOOF;
-	  break;
+    ctx->default_receiver_flags |= pf_SPOOF;
+    break;
 	case 'c': /* config file */
 	  if (read_cf_file (optarg, ctx) != 0)
 	    {
@@ -868,8 +895,9 @@ Supported options:\n\
   -t <timeout_ms>          Exit with RC 5 if no data is received for this\n\
                            amount of milliseconds\n\
   -b <size>                set socket buffer size (default %lu)\n\
-  -n			   don't compute UDP checksum (leave at 0)\n\
+  -n                       don't compute UDP checksum (leave at 0)\n\
   -S                       maintain (spoof) source addresses\n\
+  -P <address>             spoof source address with specified address\n\
   -x <delay>               transmit delay in microseconds\n\
   -c <configfile>          specify a config file to read\n\
   -f                       fork program into background\n\
diff --git a/samplicate.c b/samplicate.c
index 409ce97..a3f44fe 100644
--- a/samplicate.c
+++ b/samplicate.c
@@ -483,6 +483,16 @@ send_pdu_to_receiver (receiver, fpdu, length, source_addr)
 			       (struct sockaddr *) &receiver->addr,
 			       receiver->ttl, rawsend_flags);
     }
+  else if(receiver->flags & pf_SPOOF_WITH_IP)
+    {
+
+      int rawsend_flags
+	= ((receiver->flags & pf_CHECKSUM) ? RAWSEND_COMPUTE_UDP_CHECKSUM : 0);
+      return raw_send_from_to (receiver->fd, fpdu, length,
+			       (struct sockaddr *) &receiver->spoofed_src_addr,
+			       (struct sockaddr *) &receiver->addr,
+			       receiver->ttl, rawsend_flags);
+    }
   else
     {
       return sendto (receiver->fd, (char*) fpdu, length, 0,
@@ -539,7 +549,7 @@ make_send_sockets (struct samplicator_context *ctx)
 	  struct receiver *receiver = &sctx->receivers[i];
 	  int af = receiver->addr.ss_family;
 	  int af_index = af == AF_INET ? 0 : 1;
-	  int spoof_p = receiver->flags & pf_SPOOF;
+	  int spoof_p = receiver->flags & pf_SPOOF || receiver->flags & pf_SPOOF_WITH_IP;
 
 	  if (socks[spoof_p][af_index] == -1)
 	    {
diff --git a/samplicator.h b/samplicator.h
index 630ea11..6cd8609 100644
--- a/samplicator.h
+++ b/samplicator.h
@@ -12,6 +12,8 @@ enum receiver_flags
 {
   pf_SPOOF	= 0x0001,
   pf_CHECKSUM	= 0x0002,
+  pf_SPOOF_WITH_IP	= 0x0004,
+  
 };
 
 struct samplicator_context {
@@ -34,6 +36,8 @@ struct samplicator_context {
 
   const char		       *config_file_name;
   int				config_file_lineno;
+  
+  const char *spoofed_src_addr;
 
   /* statistics */
   uint32_t			unmatched_packets;
@@ -48,6 +52,10 @@ struct receiver {
   int				freqcount;
   int				ttl;
   enum receiver_flags		flags;
+  
+  struct sockaddr_storage spoofed_src_addr;
+  socklen_t spoofed_src_addrlen;
+  
 
   /* statistics */
   uint32_t			out_packets;