win32: pcapif: ensure we can run with npcap as well

By default, npcap keeps its DLLs not in system32 but in system32/npcap. To load DLLs from there, mark them as "delay load DLLs" and adjust the DLL search path before using/loading them. Signed-off-by: Simon Goldschmidt <goldsimon@gmx.de>
ArduPilot · Jun 29, 2023 · 1a5dffb · 1a5dffb
1 parent bfcbf80
commit 1a5dffb
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diff --git a/contrib/ports/win32/msvc/lwIP_Test.vcxproj b/contrib/ports/win32/msvc/lwIP_Test.vcxproj
@@ -85,6 +85,7 @@
       <TargetMachine>MachineX86</TargetMachine>
       <GenerateMapFile>true</GenerateMapFile>
       <MapFileName>$(TargetDir)$(TargetName).map</MapFileName>
+      <DelayLoadDLLs>Packet.dll;wpcap.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
     </Link>
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">
@@ -125,6 +126,7 @@
       <TargetMachine>MachineX86</TargetMachine>
       <GenerateMapFile>false</GenerateMapFile>
       <MapFileName>$(TargetDir)$(TargetName).map</MapFileName>
+      <DelayLoadDLLs>Packet.dll;wpcap.dll;%(DelayLoadDLLs)</DelayLoadDLLs>
     </Link>
   </ItemDefinitionGroup>
   <ItemGroup>

diff --git a/contrib/ports/win32/pcapif.c b/contrib/ports/win32/pcapif.c
@@ -1057,6 +1057,9 @@ pcapif_init(struct netif *netif)
 
   int local_index;
   SYS_ARCH_DECL_PROTECT(lev);
+
+  pcapifh_init_npcap();
+
   SYS_ARCH_PROTECT(lev);
   local_index = ethernetif_index++;
   SYS_ARCH_UNPROTECT(lev);

diff --git a/contrib/ports/win32/pcapif_helper.c b/contrib/ports/win32/pcapif_helper.c
@@ -114,6 +114,33 @@ pcapifh_free_readonly_mem(void *data)
   }
 }
 
+/**
+ * Npcap keeps its DLLs in a different directory for compatiblity with winpcap.
+ * Make sure they get found by adding that directory to the DLL search path.
+ */
+void pcapifh_init_npcap(void)
+{
+  char npcap_dir[512];
+  unsigned int len;
+  static char npcap_initialized = 0;
+
+  if (!npcap_initialized)
+  {
+    npcap_initialized = 1;
+
+    len = GetSystemDirectory(npcap_dir, 480);
+    if (!len) {
+      lwip_win32_platform_diag("Error in GetSystemDirectory: %x", GetLastError());
+      return;
+    }
+    strcat_s(npcap_dir, 512, "\\Npcap");
+    if (SetDllDirectory(npcap_dir) == 0) {
+      lwip_win32_platform_diag("Error in SetDllDirectory: %x", GetLastError());
+      return;
+    }
+  }
+}
+
 #else /* WIN32 */
 
 /* @todo: add linux/unix implementation? */
@@ -138,4 +165,8 @@ void pcapifh_linkstate_close(struct pcapifh_linkstate* state)
   LWIP_UNUSED_ARG(state);
 }
 
+void pcapifh_init_npcap(void)
+{
+}
+
 #endif /* WIN32 */
diff --git a/contrib/ports/win32/pcapif_helper.h b/contrib/ports/win32/pcapif_helper.h
@@ -22,6 +22,8 @@ void pcapifh_linkstate_close(struct pcapifh_linkstate* state);
 void *pcapifh_alloc_readonly_copy(void *data, size_t len);
 void pcapifh_free_readonly_mem(void *data);
 
+void pcapifh_init_npcap(void);
+
 #ifdef __cplusplus
 }
 #endif