handle EWOULDBLOCK. Helps with #5286

src/listen/radius/proto_radius_tcp.c

@@ -113,6 +113,23 @@ static ssize_t mod_read(fr_listen_t *li, UNUSED void **packet_ctx, fr_time_t *re
 	 */
 	data_size = read(thread->sockfd, buffer + *leftover, buffer_len - *leftover);
 	if (data_size < 0) {
+		switch (errno) {
+#if defined(EWOULDBLOCK) && (EWOULDBLOCK != EAGAIN)
+		case EWOULDBLOCK:
+#endif
+		case EAGAIN:
+			/*
+			 *	We didn't read any data leave the buffers alone.
+			 *
+			 *	i.e. if we had a partial packet in the buffer and we didn't read any data,
+			 *	then the partial packet is still left in the buffer.
+			 */
+			return 0;
+
+		default:
+			break;
+		}
+
 		PDEBUG2("proto_radius_tcp got read error %zd", data_size);
 		return data_size;
 	}

src/listen/tacacs/proto_tacacs_tcp.c

@@ -135,6 +135,23 @@ static ssize_t mod_read(fr_listen_t *li, UNUSED void **packet_ctx, fr_time_t *re
 	 */
 	data_size = read(thread->sockfd, buffer + (*leftover), buffer_len - (*leftover));
 	if (data_size < 0) {
+		switch (errno) {
+#if defined(EWOULDBLOCK) && (EWOULDBLOCK != EAGAIN)
+		case EWOULDBLOCK:
+#endif
+		case EAGAIN:
+			/*
+			 *	We didn't read any data leave the buffers alone.
+			 *
+			 *	i.e. if we had a partial packet in the buffer and we didn't read any data,
+			 *	then the partial packet is still left in the buffer.
+			 */
+			return 0;
+
+		default:
+			break;
+		}
+
 		ERROR("proto_tacacs_tcp got read error (%zd) - %s", data_size, fr_syserror(errno));
 		return data_size;
 	}