Return -1 instead of calling pfatal in nmap_raw_socket.

There was one case where we previously didn't fatal, in nse_dnet.cc.
Move the fatal calls out of nmap_raw_socket and into the calling scope,
with the exception of the one in nse_dnet.cc.

The problem was reported by Rob Nicholls.
http://seclists.org/nmap-dev/2012/q4/186

FPEngine.cc

@@ -187,6 +187,8 @@ void FPNetworkControl::init(const char *ifname, devtype iftype) {
     if (this->rawsd >= 0)
       close(this->rawsd);
     rawsd = nmap_raw_socket(ifname);
+    if (rawsd < 0)
+      pfatal("Couldn't obtain raw socket in %s", __func__);
   }
 
   /* De-register existing callers */

idle_scan.cc

@@ -383,6 +383,8 @@ static void initialize_idleproxy(struct idle_proxy_info *proxy, char *proxyName,
     proxy->ethptr = &proxy->eth;
   } else {
     proxy->rawsd = nmap_raw_socket(proxy->host.deviceName());
+    if (proxy->rawsd < 0)
+      pfatal("socket troubles in %s", __func__);
     unblock_socket(proxy->rawsd);
     proxy->eth.ethsd = NULL;
     proxy->ethptr = NULL;

osscan2.cc

@@ -1268,6 +1268,8 @@ HostOsScan::HostOsScan(Target *t) {
     rawsd = -1;
   } else {
     rawsd = nmap_raw_socket(t->deviceName());
+    if (rawsd < 0)
+      pfatal("socket troubles in %s", __func__);
     unblock_socket(rawsd);
     ethsd = NULL;
   }

scan_engine.cc

@@ -1662,6 +1662,8 @@ void UltraScanInfo::Init(std::vector<Target *> &Targets, struct scan_lists *pts,
       rawsd = -1;
     } else {
       rawsd = nmap_raw_socket(Targets[0]->deviceName());
+      if (rawsd < 0)
+        pfatal("socket troubles in %s", __func__);
       /* We do not wan't to unblock the socket since we want to wait
       if kernel send buffers fill up rather than get ENOBUF, and
       we won't be receiving on the socket anyway

tcpip.cc

@@ -155,8 +155,9 @@ int nmap_raw_socket(const char *warning_device_name) {
 #ifdef WIN32
   win32_fatal_raw_sockets(warning_device_name);
 #endif
-  if ((rawsd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0 )
-    pfatal("socket troubles in %s", __func__);
+  rawsd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
+  if (rawsd < 0)
+    return rawsd;
   broadcast_socket(rawsd);
 #ifndef WIN32
   sethdrinclude(rawsd);

traceroute.cc

@@ -879,6 +879,8 @@ TracerouteState::TracerouteState(std::vector<Target *> &targets) {
     rawsd = -1;
   } else {
     rawsd = nmap_raw_socket(targets[0]->deviceName());
+    if (rawsd < 0)
+      pfatal("traceroute: socket troubles");
     ethsd = NULL;
   }