lib: Don't silently ignore partial writes for o_stream_nsend()

Normally o_stream_nsend() should be used only for blocking streams or
streams with infinite (or "enough") buffer space.

src/lib/ostream-private.h

@@ -40,6 +40,7 @@ struct ostream_private {
 	unsigned int closing:1;
 	unsigned int last_errors_not_checked:1;
 	unsigned int error_handling_disabled:1;
+	unsigned int noverflow:1;
 };
 
 struct ostream *

src/lib/ostream.c

@@ -230,18 +230,16 @@ ssize_t o_stream_send(struct ostream *stream, const void *data, size_t size)
  	return o_stream_sendv(stream, &iov, 1);
 }
 
-ssize_t o_stream_sendv(struct ostream *stream, const struct const_iovec *iov,
-		       unsigned int iov_count)
+static ssize_t
+o_stream_sendv_int(struct ostream *stream, const struct const_iovec *iov,
+		   unsigned int iov_count, bool *overflow_r)
 {
 	struct ostream_private *_stream = stream->real_stream;
 	unsigned int i;
 	size_t total_size;
 	ssize_t ret;
 
-	if (unlikely(stream->closed || stream->stream_errno != 0)) {
-		errno = stream->stream_errno;
-		return -1;
-	}
+	*overflow_r = FALSE;
 
 	for (i = 0, total_size = 0; i < iov_count; i++)
 		total_size += iov[i].iov_len;
@@ -255,11 +253,24 @@ ssize_t o_stream_sendv(struct ostream *stream, const struct const_iovec *iov,
 			errno = stream->stream_errno;
 		} else {
 			stream->overflow = TRUE;
+			*overflow_r = TRUE;
 		}
 	}
 	return ret;
 }
 
+ssize_t o_stream_sendv(struct ostream *stream, const struct const_iovec *iov,
+		       unsigned int iov_count)
+{
+	bool overflow;
+
+	if (unlikely(stream->closed || stream->stream_errno != 0)) {
+		errno = stream->stream_errno;
+		return -1;
+	}
+	return o_stream_sendv_int(stream, iov, iov_count, &overflow);
+}
+
 ssize_t o_stream_send_str(struct ostream *stream, const char *str)
 {
 	return o_stream_send(stream, str, strlen(str));
@@ -279,9 +290,14 @@ void o_stream_nsend(struct ostream *stream, const void *data, size_t size)
 void o_stream_nsendv(struct ostream *stream, const struct const_iovec *iov,
 		     unsigned int iov_count)
 {
-	if (unlikely(stream->closed || stream->stream_errno != 0))
+	bool overflow;
+
+	if (unlikely(stream->closed || stream->stream_errno != 0 ||
+		     stream->real_stream->noverflow))
 		return;
-	(void)o_stream_sendv(stream, iov, iov_count);
+	(void)o_stream_sendv_int(stream, iov, iov_count, &overflow);
+	if (overflow)
+		stream->real_stream->noverflow = TRUE;
 	stream->real_stream->last_errors_not_checked = TRUE;
 }
 
@@ -302,6 +318,12 @@ int o_stream_nfinish(struct ostream *stream)
 {
 	o_stream_nflush(stream);
 	o_stream_ignore_last_errors(stream);
+	if (stream->stream_errno == 0 && stream->real_stream->noverflow) {
+		io_stream_set_error(&stream->real_stream->iostream,
+			"Output stream buffer was full (%"PRIuSIZE_T" bytes)",
+			o_stream_get_max_buffer_size(stream));
+		stream->stream_errno = ENOBUFS;
+	}
 	return stream->stream_errno != 0 ? -1 : 0;
 }
 

src/lib/ostream.h

@@ -119,16 +119,19 @@ ssize_t o_stream_send(struct ostream *stream, const void *data, size_t size);
 ssize_t o_stream_sendv(struct ostream *stream, const struct const_iovec *iov,
 		       unsigned int iov_count);
 ssize_t o_stream_send_str(struct ostream *stream, const char *str);
-/* Send with delayed error handling. o_stream_has_errors() or
+/* Send with delayed error handling. o_stream_nfinish() or
    o_stream_ignore_last_errors() must be called after these functions before
-   the stream is destroyed. */
+   the stream is destroyed. If any of the data can't be sent due to stream's
+   buffer getting full, all further nsends are ignores and o_stream_nfinish()
+   will fail. */
 void o_stream_nsend(struct ostream *stream, const void *data, size_t size);
 void o_stream_nsendv(struct ostream *stream, const struct const_iovec *iov,
 		     unsigned int iov_count);
 void o_stream_nsend_str(struct ostream *stream, const char *str);
 void o_stream_nflush(struct ostream *stream);
-/* Flushes the stream and returns -1 if stream->stream_errno is non-zero.
-   Marks the stream's error handling as completed. */
+/* Marks the stream's error handling as completed. Flushes the stream and
+   returns -1 if stream->stream_errno is non-zero. Returns failure if any of
+   the o_stream_nsend*() didn't write all data. */
 int o_stream_nfinish(struct ostream *stream);
 /* Marks the stream's error handling as completed to avoid i_panic() on
    destroy. */