From eb9bcb64185ac155c02cc1a604692c4b00368324 Mon Sep 17 00:00:00 2001
From: Felix Fietkau <nbd@nbd.name>
Date: Fri, 29 Mar 2024 10:23:28 +0100
Subject: [PATCH] ustream: prevent recursive calls to the read callback

Simplifies stacked ustreams and calling poll from the read function.
Reuse an unused leftover struct member in order to not break ABI.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
 ustream.c | 14 ++++++++++----
 ustream.h |  3 ++-
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/ustream.c b/ustream.c
index d36ce08..d200dba 100644
--- a/ustream.c
+++ b/ustream.c
@@ -24,6 +24,8 @@
 
 #include "ustream.h"
 
+#define CB_PENDING_READ	(1 << 0)
+
 static void ustream_init_buf(struct ustream_buf *buf, int len)
 {
 	if (!len)
@@ -133,7 +135,6 @@ void ustream_init_defaults(struct ustream *s)
 	s->state_change.cb = ustream_state_change_cb;
 	s->write_error = false;
 	s->eof = false;
-	s->eof_write_done = false;
 	s->read_blocked = 0;
 
 	s->r.buffers = 0;
@@ -301,7 +302,6 @@ char *ustream_reserve(struct ustream *s, int len, int *maxlen)
 void ustream_fill_read(struct ustream *s, int len)
 {
 	struct ustream_buf *buf = s->r.data_tail;
-	int n = len;
 	int maxlen;
 
 	s->r.data_bytes += len;
@@ -321,8 +321,14 @@ void ustream_fill_read(struct ustream *s, int len)
 		buf = buf->next;
 	} while (len);
 
-	if (s->notify_read)
-		s->notify_read(s, n);
+	if (s->notify_read) {
+		if (s->pending_cb & CB_PENDING_READ)
+			return;
+
+		s->pending_cb |= CB_PENDING_READ;
+		s->notify_read(s, s->r.data_bytes);
+		s->pending_cb &= ~CB_PENDING_READ;
+	}
 }
 
 char *ustream_get_read_buf(struct ustream *s, int *buflen)
diff --git a/ustream.h b/ustream.h
index 9a30618..b8443e5 100644
--- a/ustream.h
+++ b/ustream.h
@@ -114,7 +114,8 @@ struct ustream {
 	 */
 	bool string_data;
 	bool write_error;
-	bool eof, eof_write_done;
+	bool eof;
+	uint8_t pending_cb;
 
 	enum read_blocked_reason read_blocked;
 };