hooklib: add adapter_hook_override to allow specifying network adapter id

src/main/hooklib/adapter.c

@@ -3,12 +3,16 @@
 #include <windows.h>
 #include <winsock2.h>
 
+#include <stdbool.h>
+#include <string.h>
+
 #include "hook/table.h"
 
 #include "hooklib/adapter.h"
 
 #include "util/codepage.h"
 #include "util/defs.h"
+#include "util/log.h"
 
 static DWORD WINAPI
 my_GetAdaptersInfo(PIP_ADAPTER_INFO adapter_info, PULONG out_buf_len);
@@ -16,6 +20,9 @@ my_GetAdaptersInfo(PIP_ADAPTER_INFO adapter_info, PULONG out_buf_len);
 static DWORD(WINAPI *real_GetAdaptersInfo)(
     PIP_ADAPTER_INFO adapter_info, PULONG out_buf_len);
 
+static IP_ADDRESS_STRING override_address;
+static bool use_address_override;
+
 static const struct hook_symbol adapter_hook_syms[] = {
     {.name = "GetAdaptersInfo",
      .patch = my_GetAdaptersInfo,
@@ -37,6 +44,24 @@ my_GetAdaptersInfo(PIP_ADAPTER_INFO adapter_info, PULONG out_buf_len)
         return ret;
     }
 
+    info = adapter_info;
+
+    if (use_address_override) {
+        while (info) {
+            // this is well defined to be at most sizeof(IP_ADDRESS_STRING)
+            // and NULL filled if shorter (hence the memset in adapter_hook_override)
+            if (!memcmp(info->IpAddressList.IpAddress.String, override_address.String, sizeof(IP_ADDRESS_STRING))) {
+                log_info("%s: using [override] adapter: %s, %s, %s, %s", __FUNCTION__, info->AdapterName, info->Description, info->IpAddressList.IpAddress.String, info->IpAddressList.IpMask.String);
+
+                // copy only this adapter over
+                memcpy(adapter_info, info, sizeof(*info));
+                adapter_info->Next = 0;
+                return ret;
+            }
+            info = info->Next;
+        }
+    }
+
     ip_fwd_table = (MIB_IPFORWARDTABLE *) malloc(sizeof(MIB_IPFORWARDTABLE));
     table_size = 0;
 
@@ -58,6 +83,9 @@ my_GetAdaptersInfo(PIP_ADAPTER_INFO adapter_info, PULONG out_buf_len)
 
     while (info) {
         if (info->Index == best_adapter) {
+            log_info("%s: using [best] adapter: %s, %s, %s, %s", __FUNCTION__, info->AdapterName, info->Description, info->IpAddressList.IpAddress.String, info->IpAddressList.IpMask.String);
+
+            // copy only this adapter over
             memcpy(adapter_info, info, sizeof(*info));
             adapter_info->Next = 0;
             return ret;
@@ -73,3 +101,24 @@ void adapter_hook_init(void)
     hook_table_apply(
         NULL, "iphlpapi.dll", adapter_hook_syms, lengthof(adapter_hook_syms));
 }
+
+void adapter_hook_override(const char* adapter_address)
+{
+    // starts off false anyways due to static
+    // but in case it gets called multiple times, set it anyways
+    use_address_override = false;
+
+    if (adapter_address == NULL || *adapter_address == NULL) {
+        // empty, do nothing
+        return;
+    }
+    if (strlen(adapter_address) > sizeof(IP_ADDRESS_STRING)) {
+        log_warning("%s: %s is not an ipv4 address", __FUNCTION__, adapter_address);
+        return;
+    }
+
+    memset(override_address.String, 0, sizeof(IP_ADDRESS_STRING));
+    memcpy(override_address.String, adapter_address, sizeof(IP_ADDRESS_STRING));
+
+    use_address_override = true;
+}