Made WinDump use Npcap when Npcap and WinPcap coexist.

There are two steps:
1) Add "wpcap.dll" to the "DelayLoadDLLs" of the project file.
2) Call init_npcap_dll_path() before you use any wpcap.dll functions, the beginning of the main() function is a good place.

Author: hsluoyz

Tcpdump.c

@@ -443,6 +443,26 @@ static int tcpdump_printf(netdissect_options *ndo _U_,
   return ret;
 }
 
+static void init_npcap_dll_path()
+{
+	BOOL(WINAPI *SetDllDirectory)(LPCTSTR);
+	char sysdir_name[512];
+	int len;
+
+	SetDllDirectory = (BOOL(WINAPI *)(LPCTSTR)) GetProcAddress(GetModuleHandle("kernel32.dll"), "SetDllDirectoryA");
+	if (SetDllDirectory == NULL) {
+		error("Error in SetDllDirectory");
+	}
+	else {
+		len = GetSystemDirectory(sysdir_name, 480);	//	be safe
+		if (!len)
+			error("Error in GetSystemDirectory (%d)", GetLastError());
+		strcat(sysdir_name, "\\Npcap");
+		if (SetDllDirectory(sysdir_name) == 0)
+			error("Error in SetDllDirectory(\"System32\\Npcap\")");
+	}
+}
+
 int
 main(int argc, char **argv)
 {
@@ -466,6 +486,9 @@ main(int argc, char **argv)
 	int devnum;
 #endif
 	int status;
+
+	init_npcap_dll_path();
+
 #ifdef WIN32
 	u_int UserBufferSize = 1000000;
 	if(wsockinit() != 0) return 1;

win32/prj/WinDump.vcxproj

@@ -135,6 +135,7 @@
       <DataExecutionPrevention>
       </DataExecutionPrevention>
       <TargetMachine>MachineX86</TargetMachine>
+      <DelayLoadDLLs>wpcap.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
     </Link>
     <Bscmake>
       <SuppressStartupBanner>true</SuppressStartupBanner>
@@ -176,6 +177,7 @@
       <DataExecutionPrevention>
       </DataExecutionPrevention>
       <TargetMachine>MachineX86</TargetMachine>
+      <DelayLoadDLLs>wpcap.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
     </Link>
     <Bscmake>
       <SuppressStartupBanner>true</SuppressStartupBanner>
@@ -221,6 +223,7 @@
       <DataExecutionPrevention>
       </DataExecutionPrevention>
       <TargetMachine>MachineX64</TargetMachine>
+      <DelayLoadDLLs>wpcap.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
     </Link>
     <Bscmake>
       <SuppressStartupBanner>true</SuppressStartupBanner>
@@ -263,6 +266,7 @@
       <DataExecutionPrevention>
       </DataExecutionPrevention>
       <TargetMachine>MachineX64</TargetMachine>
+      <DelayLoadDLLs>wpcap.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
     </Link>
     <Bscmake>
       <SuppressStartupBanner>true</SuppressStartupBanner>