solved the problem that Windows cannot multicast (#576)

* Solve the problem that Windows cannot multicast.

* Better git judgment logic.

CMakeLists.txt

@@ -7,13 +7,14 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 # N2n release information
 set(N2N_VERSION "2.9.0")
-set(N2N_OSNAME ${CMAKE_SYSTEM})
+set(N2N_OSNAME ${CMAKE_SYSTEM_NAME})
 execute_process(
-        COMMAND git --version
+        COMMAND git status
         WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
-        OUTPUT_VARIABLE GIT_EXIST
+        OUTPUT_VARIABLE GIT_OUTPUT
+        RESULT_VARIABLE GIT_ERROR_CODE
 )
-if (GIT_EXIST)
+if (GIT_ERROR_CODE EQUAL 0)
 execute_process(
         COMMAND git rev-list --count HEAD
         WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}
@@ -28,7 +29,7 @@ string(REGEX REPLACE "\n$" "" GIT_REV "${GIT_REV}")
 string(REGEX REPLACE "\n$" "" GIT_ID "${GIT_ID}")
 set(N2N_VERSION "${N2N_VERSION}.r${GIT_REV}.${GIT_ID}")
 MESSAGE(STATUS "Build from git rev: ${N2N_VERSION}")
-endif (GIT_EXIST)
+endif (GIT_ERROR_CODE EQUAL 0)
 
 add_definitions(-DCMAKE_BUILD)
 add_definitions(-DGIT_RELEASE="${N2N_VERSION}" -DPACKAGE_VERSION="${N2N_VERSION}" -DPACKAGE_OSNAME="${N2N_OSNAME}")
@@ -142,7 +143,7 @@ endif(N2N_OPTION_USE_ZSTD)
 if(DEFINED WIN32)
   add_library(edge_utils_win32 src/edge_utils_win32.c)
   add_subdirectory(win32)
-  target_link_libraries(n2n edge_utils_win32 n2n_win32 )
+  target_link_libraries(n2n edge_utils_win32 n2n_win32 iphlpapi)
 endif(DEFINED WIN32)
 
 add_executable(edge src/edge.c)
@@ -164,7 +165,7 @@ if(N2N_OPTION_USE_PCAPLIB AND (NOT DEFINED WIN32))
   # Linux Capabilities
   find_library(CAP_LIB cap)
   if(CAP_LIB)
-    target_link_libraries(edge cap)
+    target_link_libraries(edge cap.a)
     set(CMAKE_REQUIRED_LIBRARIES ${CAP_LIB})
     ADD_DEFINITIONS("-DHAVE_LIBCAP")
   endif()

include/edge_utils_win32.h

@@ -25,10 +25,17 @@
 
 #include <process.h>
 #include <n2n.h>
+#include <winsock2.h>
+#include <iphlpapi.h>
 
 
 /* Multicast peers discovery disabled due to https://github.com/ntop/n2n/issues/65 */
-#define SKIP_MULTICAST_PEERS_DISCOVERY
+
+/* Currently, multicast is performed by specifying the default routing network adapter.
+ * If the solution is determined to be stable and effective,
+ * all macro definitions "SKIP_MULTICAST_PEERS_DISCOVERY" will be completely deleted in the future.
+ */
+//#define SKIP_MULTICAST_PEERS_DISCOVERY
 
 struct tunread_arg {
     n2n_edge_t *eee;
@@ -36,6 +43,7 @@ struct tunread_arg {
 };
 
 extern HANDLE startTunReadThread (struct tunread_arg *arg);
+int get_best_interface_ip(n2n_edge_t * eee, dec_ip_str_t ip_addr);
 
 
 #endif /* WIN32 */

src/edge_utils.c

@@ -718,6 +718,9 @@ static ssize_t sendto_sock (int fd, const void * buf,
     if(sent < 0) {
         char * c = strerror(errno);
         traceEvent(TRACE_ERROR, "sendto failed (%d) %s", errno, c);
+#ifdef WIN32
+        traceEvent(TRACE_ERROR, "WSAGetLastError(): %u", WSAGetLastError());
+#endif
     } else {
         traceEvent(TRACE_DEBUG, "sendto sent=%d to ", (signed int)sent);
     }
@@ -734,7 +737,13 @@ static void check_join_multicast_group (n2n_edge_t *eee) {
     if(!eee->multicast_joined) {
         struct ip_mreq mreq;
         mreq.imr_multiaddr.s_addr = inet_addr(N2N_MULTICAST_GROUP);
+#ifdef WIN32
+        dec_ip_str_t ip_addr;
+        get_best_interface_ip(eee, ip_addr);
+        mreq.imr_interface.s_addr = inet_addr(ip_addr);
+#else
         mreq.imr_interface.s_addr = htonl(INADDR_ANY);
+#endif
 
         if(setsockopt(eee->udp_multicast_sock, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&mreq, sizeof(mreq)) < 0) {
             traceEvent(TRACE_WARNING, "Failed to bind to local multicast group %s:%u [errno %u]",

src/edge_utils_win32.c

@@ -48,5 +48,65 @@ HANDLE startTunReadThread (struct tunread_arg *arg) {
                         0,             /* thread creation flags */
                         &dwThreadId)); /* thread id out */
 }
+
+
+
+int get_best_interface_ip(n2n_edge_t * eee, dec_ip_str_t ip_addr){
+    DWORD interface_index = -1;
+    DWORD dwRetVal = 0;
+    PIP_ADAPTER_INFO pAdapterInfo = NULL, pAdapter = NULL;
+    macstr_t mac_buf;
+    ULONG ulOutBufLen = sizeof(IP_ADAPTER_INFO);
+
+    dwRetVal = GetBestInterface(*(IPAddr*)(&eee->curr_sn->sock.addr.v4), &interface_index);
+    if(dwRetVal != NO_ERROR) return -1;
+
+    pAdapterInfo = (PIP_ADAPTER_INFO)malloc(ulOutBufLen);
+    if (pAdapterInfo == NULL) {
+        traceEvent(TRACE_INFO, "Error allocating memory needed to call GetAdaptersInfo\n");
+        return -1;
+    }
+
+    dwRetVal = GetAdaptersInfo(pAdapterInfo, &ulOutBufLen);
+    if(dwRetVal == ERROR_BUFFER_OVERFLOW){
+        pAdapterInfo = (PIP_ADAPTER_INFO)realloc(pAdapterInfo, ulOutBufLen);
+        if (pAdapterInfo == NULL) {
+            traceEvent(TRACE_INFO, "Error allocating memory needed to call GetAdaptersInfo\n");
+            return -1;
+        }
+    }
+
+    dwRetVal = GetAdaptersInfo(pAdapterInfo, &ulOutBufLen);
+//    hexdump((uint8_t*)pAdapterInfo, ulOutBufLen);
+    if (dwRetVal == NO_ERROR) {
+        for(pAdapter = pAdapterInfo; pAdapter != NULL; pAdapter = pAdapter->Next){
+            if (pAdapter->Index != interface_index) continue;
+
+            traceEvent(TRACE_DEBUG, "Adapter Index: %ld\n", pAdapter->Index);
+            traceEvent(TRACE_DEBUG, "Combo Index:   %ld\n", pAdapter->ComboIndex);
+            traceEvent(TRACE_DEBUG, "Adapter Name:  %s\n", pAdapter->AdapterName);
+            traceEvent(TRACE_DEBUG, "Adapter Desc:  %s\n", pAdapter->Description);
+            traceEvent(TRACE_DEBUG, "Adapter Type:  %u\n", pAdapter->Type);
+            macaddr_str(mac_buf, pAdapter->Address);
+            traceEvent(TRACE_DEBUG, "Adapter Addr:  %s\n", mac_buf);
+            traceEvent(TRACE_DEBUG, "DHCP Enabled:  %u\n", pAdapter->DhcpEnabled);
+            traceEvent(TRACE_DEBUG, "DHCP Server:   %s\n", pAdapter->DhcpServer.IpAddress.String);
+            traceEvent(TRACE_DEBUG, "IP Address:    %s\n", pAdapter->IpAddressList.IpAddress.String);
+            traceEvent(TRACE_DEBUG, "IP Mask:       %s\n", pAdapter->IpAddressList.IpMask.String);
+            traceEvent(TRACE_DEBUG, "Gateway:       %s\n", pAdapter->GatewayList.IpAddress.String);
+            strncpy(ip_addr, pAdapter->IpAddressList.IpAddress.String, sizeof(dec_ip_str_t)-1);
+        }
+    }
+    else {
+        traceEvent(TRACE_WARNING, "GetAdaptersInfo failed with error: %d\n", dwRetVal);
+    }
+    if (pAdapterInfo != NULL){
+        free(pAdapterInfo);
+        pAdapterInfo = NULL;
+    }
+    return 0;
+}
+
+
 #endif