Guard TCP API writes against dead sockets

Agent-Logs-Url: https://github.com/meshtastic/firmware/sessions/ebeb38d5-7339-4eac-b310-4b6dd9d40758

Co-authored-by: thebentern <9000580+thebentern@users.noreply.github.com>

src/mesh/StreamAPI.cpp

@@ -52,7 +52,8 @@ void StreamAPI::writeStream()
         do {
             // Send every packet we can
             len = getFromRadio(txBuf + HEADER_LEN);
-            emitTxBuffer(len);
+            if (len != 0 && !emitTxBuffer(len))
+                break;
         } while (len);
     }
 }
@@ -169,21 +170,41 @@ int32_t StreamAPI::readStream()
 /**
  * Send the current txBuffer over our stream
  */
-void StreamAPI::emitTxBuffer(size_t len)
+bool StreamAPI::writeFrame(uint8_t *buf, size_t len)
 {
-    if (len != 0) {
-        txBuf[0] = START1;
-        txBuf[1] = START2;
-        txBuf[2] = (len >> 8) & 0xff;
-        txBuf[3] = len & 0xff;
+    if (len == 0 || !canWrite)
+        return false;
 
-        auto totalLen = len + HEADER_LEN;
+    buf[0] = START1;
+    buf[1] = START2;
+    buf[2] = (len >> 8) & 0xff;
+    buf[3] = len & 0xff;
+
+    auto totalLen = len + HEADER_LEN;
+    if (!canWriteFrame(totalLen))
+        return false;
+
+    size_t written;
+    {
         // Serialize stream writes against `emitLogRecord` so a LOG_ firing
         // mid-packet-emission can't interleave bytes on the wire.
         concurrency::LockGuard guard(&streamLock);
-        stream->write(txBuf, totalLen);
-        stream->flush();
+        written = stream->write(buf, totalLen);
+        if (written == totalLen)
+            stream->flush();
     }
+
+    if (written != totalLen) {
+        onFrameWriteFailed(totalLen, written);
+        return false;
+    }
+
+    return true;
+}
+
+bool StreamAPI::emitTxBuffer(size_t len)
+{
+    return writeFrame(txBuf, len);
 }
 
 void StreamAPI::emitRebooted()
@@ -221,20 +242,7 @@ void StreamAPI::emitLogRecord(meshtastic_LogRecord_Level level, const char *src,
 
     size_t len =
         pb_encode_to_bytes(txBufLog + HEADER_LEN, meshtastic_FromRadio_size, &meshtastic_FromRadio_msg, &fromRadioScratchLog);
-    if (len != 0) {
-        txBufLog[0] = START1;
-        txBufLog[1] = START2;
-        txBufLog[2] = (len >> 8) & 0xff;
-        txBufLog[3] = len & 0xff;
-
-        auto totalLen = len + HEADER_LEN;
-        // Serialize stream writes against `emitTxBuffer` so a packet
-        // emission in flight on another task doesn't interleave bytes
-        // with this log record.
-        concurrency::LockGuard guard(&streamLock);
-        stream->write(txBufLog, totalLen);
-        stream->flush();
-    }
+    writeFrame(txBufLog, len);
 }
 
 /// Hookable to find out when connection changes
@@ -249,4 +257,4 @@ void StreamAPI::onConnectionChanged(bool connected)
         // received a packet in a while
         powerFSM.trigger(EVENT_SERIAL_DISCONNECTED);
     }
-}
+}