Fix critical VNC pipe bug and add debug logging

- Fix pipe handling in vnc.c: was writing to read end instead of write end
- Add separate read_fd/write_fd fields to vnc_session_t struct
- Add debug logging for VNC data exchange in websocket handler
- Add hex dump logging for VNC pipe communication

This resolves the 'Wrote -1 bytes to pipe' error that was preventing
VNC connections from working properly.

wssshd2/vnc.c

@@ -40,19 +40,29 @@ static void *read_pipe_output(void *arg) {
 
     while (1) {
         FD_ZERO(&readfds);
-        FD_SET(session->master_fd, &readfds);
+        FD_SET(session->read_fd, &readfds);
 
         tv.tv_sec = 0;
         tv.tv_usec = 100000; // 100ms timeout
 
-        int ret = select(session->master_fd + 1, &readfds, NULL, NULL, &tv);
+        int ret = select(session->read_fd + 1, &readfds, NULL, NULL, &tv);
         if (ret < 0) break;
         if (ret == 0) continue; // timeout
 
-        if (FD_ISSET(session->master_fd, &readfds)) {
-            ssize_t bytes_read = read(session->master_fd, buffer, sizeof(buffer));
+        if (FD_ISSET(session->read_fd, &readfds)) {
+            ssize_t bytes_read = read(session->read_fd, buffer, sizeof(buffer));
             if (bytes_read <= 0) break;
 
+            if (session->debug_vnc) {
+                printf("VNC: Received %zd bytes from pipe\n", bytes_read);
+                // Debug: print first 20 bytes in hex
+                printf("VNC received data (first 20 bytes): ");
+                for (ssize_t i = 0; i < bytes_read && i < 20; i++) {
+                    printf("%02x ", (unsigned char)buffer[i]);
+                }
+                printf("\n");
+            }
+
             // Append to session output buffer
             pthread_mutex_lock(&session->output_mutex);
             if (session->output_used + bytes_read > session->output_size) {
@@ -79,7 +89,7 @@ static void *read_pipe_output(void *arg) {
     return NULL;
 }
 
-vnc_session_t *vnc_create_session(const wssshd_config_t *config, const char *client_id, const char *username) {
+vnc_session_t *vnc_create_session(const wssshd_config_t *config, const char *client_id, const char *username, bool debug_vnc) {
     vnc_session_t *session = calloc(1, sizeof(vnc_session_t));
     if (!session) return NULL;
 
@@ -104,6 +114,7 @@ vnc_session_t *vnc_create_session(const wssshd_config_t *config, const char *cli
     }
     session->output_size = 4096;
     session->output_used = 0;
+    session->debug_vnc = debug_vnc;
     pthread_mutex_init(&session->output_mutex, NULL);
 
     // Create pipe for communication
@@ -114,7 +125,8 @@ vnc_session_t *vnc_create_session(const wssshd_config_t *config, const char *cli
         return NULL;
     }
 
-    session->master_fd = pipefd[0]; // read end
+    session->read_fd = pipefd[0];  // read end
+    session->write_fd = pipefd[1]; // write end
 
     // Build command: wsssht --pipe --wssshd-port 9898 vnc://{client_id}@mbetter.nexlab.net
     char command[1024];
@@ -143,8 +155,7 @@ vnc_session_t *vnc_create_session(const wssshd_config_t *config, const char *cli
         _exit(1); // Should not reach here
     }
 
-    // Parent process
-    close(pipefd[1]); // close write end
+    // Parent process keeps both ends: read_fd for reading from child, write_fd for writing to child
     session->proc_pid = pid;
 
     // Start output reading thread
@@ -158,8 +169,11 @@ vnc_session_t *vnc_create_session(const wssshd_config_t *config, const char *cli
 void vnc_free_session(vnc_session_t *session) {
     if (!session) return;
 
-    if (session->master_fd >= 0) {
-        close(session->master_fd);
+    if (session->read_fd >= 0) {
+        close(session->read_fd);
+    }
+    if (session->write_fd >= 0) {
+        close(session->write_fd);
     }
 
     if (session->output_buffer) {
@@ -171,14 +185,27 @@ void vnc_free_session(vnc_session_t *session) {
 }
 
 bool vnc_send_data(vnc_session_t *session, const char *data, size_t len) {
-    if (!session || session->master_fd < 0) return false;
+    if (!session || session->write_fd < 0) return false;
 
     // Check if process is still running
     if (waitpid(session->proc_pid, NULL, WNOHANG) > 0) {
         return false;
     }
 
-    ssize_t written = write(session->master_fd, data, len);
+    if (session->debug_vnc) {
+        printf("VNC: Sending %zu bytes to pipe\n", len);
+        // Debug: print first 20 bytes in hex
+        printf("VNC send data (first 20 bytes): ");
+        for (size_t i = 0; i < len && i < 20; i++) {
+            printf("%02x ", (unsigned char)data[i]);
+        }
+        printf("\n");
+    }
+
+    ssize_t written = write(session->write_fd, data, len);
+    if (session->debug_vnc) {
+        printf("VNC: Wrote %zd bytes to pipe\n", written);
+    }
     return written > 0;
 }
 

wssshd2/vnc.h

@@ -29,15 +29,17 @@ typedef struct {
     char client_id[256];
     char username[50];
     int proc_pid;
-    int master_fd; // pipe fd
+    int read_fd;  // pipe read end
+    int write_fd; // pipe write end
     bool active;
+    bool debug_vnc;
     char *output_buffer;
     size_t output_size;
     size_t output_used;
     pthread_mutex_t output_mutex;
 } vnc_session_t;
 
-vnc_session_t *vnc_create_session(const wssshd_config_t *config, const char *client_id, const char *username);
+vnc_session_t *vnc_create_session(const wssshd_config_t *config, const char *client_id, const char *username, bool debug_vnc);
 void vnc_free_session(vnc_session_t *session);
 bool vnc_send_data(vnc_session_t *session, const char *data, size_t len);
 char *vnc_get_output(vnc_session_t *session, size_t *len);

wssshd2/web.c

@@ -321,7 +321,7 @@ static void *websocket_vnc_handler(void *arg) {
         printf("[DEBUG] Launching wsssht for VNC client %s\n", ws_conn->client_id);
     }
 
-    vnc_session_t *session = vnc_create_session(global_config, ws_conn->client_id, ws_conn->username);
+    vnc_session_t *session = vnc_create_session(global_config, ws_conn->client_id, ws_conn->username, global_config->debug_vnc);
     if (!session) {
         printf("Failed to create VNC session for client: %s\n", ws_conn->client_id);
         ws_send_frame(ws_conn->ws_conn, WS_OPCODE_TEXT, "{\"error\":\"Failed to launch VNC session\"}", 40);
@@ -366,6 +366,13 @@ static void *websocket_vnc_handler(void *arg) {
         char *output = vnc_get_output(session, &output_len);
         if (output && output_len > 0) {
             printf("WebSocket sending %zu bytes of VNC output for request_id: %s\n", output_len, ws_conn->request_id);
+            if (global_config->debug_vnc) {
+                printf("VNC output data (first 20 bytes): ");
+                for (size_t i = 0; i < output_len && i < 20; i++) {
+                    printf("%02x ", (unsigned char)output[i]);
+                }
+                printf("\n");
+            }
             ws_send_frame(ws_conn->ws_conn, WS_OPCODE_BINARY, output, output_len);
             free(output);
         }
@@ -379,6 +386,13 @@ static void *websocket_vnc_handler(void *arg) {
             if (opcode == WS_OPCODE_BINARY && len > 0) {
                 // VNC input data
                 printf("WebSocket received %zu bytes of VNC input for request_id: %s\n", len, ws_conn->request_id);
+                if (global_config->debug_vnc) {
+                    printf("VNC input data (first 20 bytes): ");
+                    for (size_t i = 0; i < len && i < 20; i++) {
+                        printf("%02x ", (unsigned char)((const char *)data)[i]);
+                    }
+                    printf("\n");
+                }
                 vnc_send_data(session, (const char *)data, len);
             } else if (opcode == WS_OPCODE_CLOSE) {
                 // Connection closed