Centralize default stream input capacity with batch overhead

src/stream/stream.c

@@ -599,7 +599,7 @@ int stream_publish_open(struct UTUN_INSTANCE *inst, uint64_t group_id, const str
     int result = stream_open_check(inst, group_id, out);
     if (result != STREAM_OK) return result;
     struct stream_descriptor d = {.group_id = group_id, .source_node_id = inst->node_id,
-        .n = parameters ? parameters->n : 8, .r = parameters ? parameters->r : 2,
+        .n = parameters ? parameters->n : STREAM_DEFAULT_N, .r = parameters ? parameters->r : STREAM_DEFAULT_R,
         .block_size = parameters ? parameters->block_size : STREAM_RS_DEFAULT_SIZE};
     do {
         if (random_bytes((uint8_t *)&d.source_epoch, sizeof(d.source_epoch)) != 0) {

src/stream/stream_proto.h

@@ -31,6 +31,10 @@
 #define STREAM_BATCH_OVERHEAD (STREAM_BATCH_HEADER + SC_SIGN_SIZE)
 #define STREAM_BLOCK_DEFAULT_SIZE 1300
 #define STREAM_RS_DEFAULT_SIZE (STREAM_BLOCK_DEFAULT_SIZE - STREAM_BLOCK_OVERHEAD)
+#define STREAM_DEFAULT_N 8
+#define STREAM_DEFAULT_R 2
+#define STREAM_DEFAULT_INPUT_CAPACITY \
+    ((STREAM_DEFAULT_N - STREAM_DEFAULT_R) * (STREAM_RS_DEFAULT_SIZE - RS_HEADER_SIZE) - STREAM_BATCH_OVERHEAD)
 #define STREAM_BLOCK_MAX_SIZE (RS_MAX_BLOCK_SIZE + STREAM_BLOCK_OVERHEAD)
 #define STREAM_BLOCK_TIME_RESET 0x01
 #define STREAM_BUFFER_BYTES (32u * 1024u * 1024u)