From 71179a3ea97ea46b28788dfab557c675ec3f3a1e Mon Sep 17 00:00:00 2001
From: Christopher Faulet <cfaulet@haproxy.com>
Date: Fri, 7 Feb 2020 16:40:33 +0100
Subject: [PATCH] MINOR: filters: Forward data only if the last filter forwards
 something

In flt_tcp_payload() and flt_http_payload(), if the last filter does not
forwarding anything, nothing is forwarded, not even the already filtered
data. For now, this patch is useless because the last filter is always sync with
the stream's offset. But it will be mandatory for a bugfix.
---
 src/filters.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/filters.c b/src/filters.c
index 090146e68..ce6a78e05 100644
--- a/src/filters.c
+++ b/src/filters.c
@@ -611,7 +611,7 @@ flt_http_payload(struct stream *s, struct http_msg *msg, unsigned int len)
 	struct filter *filter;
 	unsigned long long *strm_off = &FLT_STRM_OFF(s, msg->chn);
 	unsigned int out = co_data(msg->chn);
-	int ret = len - out;
+	int ret = 0, data = len - out;
 
 	DBG_TRACE_ENTER(STRM_EV_STRM_ANA|STRM_EV_HTTP_ANA|STRM_EV_FLT_ANA, s, s->txn, msg);
 	list_for_each_entry(filter, &strm_flt(s)->filters, list) {
@@ -623,14 +623,19 @@ flt_http_payload(struct stream *s, struct http_msg *msg, unsigned int len)
 			unsigned int offset = *flt_off - *strm_off;
 
 			DBG_TRACE_DEVEL(FLT_ID(filter), STRM_EV_HTTP_ANA|STRM_EV_FLT_ANA, s);
-			ret = FLT_OPS(filter)->http_payload(s, filter, msg, out + offset, ret - offset);
+			ret = FLT_OPS(filter)->http_payload(s, filter, msg, out + offset, data - offset);
 			if (ret < 0)
 				goto end;
 			*flt_off += ret;
-			ret += offset;
+			data = ret + offset;
 		}
 	}
-	*strm_off += ret;
+
+	/* Only forward data if the last filter decides to forward something */
+	if (ret > 0) {
+		ret = data;
+		*strm_off += ret;
+	}
  end:
 	DBG_TRACE_LEAVE(STRM_EV_STRM_ANA|STRM_EV_HTTP_ANA|STRM_EV_FLT_ANA, s);
 	return ret;
@@ -861,7 +866,7 @@ flt_tcp_payload(struct stream *s, struct channel *chn, unsigned int len)
 	struct filter *filter;
 	unsigned long long *strm_off = &FLT_STRM_OFF(s, chn);
 	unsigned int out = co_data(chn);
-	int ret = len - out;
+	int ret = 0, data = len - out;
 
 	DBG_TRACE_ENTER(STRM_EV_TCP_ANA|STRM_EV_FLT_ANA, s);
 	list_for_each_entry(filter, &strm_flt(s)->filters, list) {
@@ -873,14 +878,19 @@ flt_tcp_payload(struct stream *s, struct channel *chn, unsigned int len)
 			unsigned int offset = *flt_off - *strm_off;
 
 			DBG_TRACE_DEVEL(FLT_ID(filter), STRM_EV_TCP_ANA|STRM_EV_FLT_ANA, s);
-			ret = FLT_OPS(filter)->tcp_payload(s, filter, chn, out + offset, ret - offset);
+			ret = FLT_OPS(filter)->tcp_payload(s, filter, chn, out + offset, data - offset);
 			if (ret < 0)
 				goto end;
 			*flt_off += ret;
-			ret += offset;
+			data = ret + offset;
 		}
 	}
-	*strm_off += ret;
+
+	/* Only forward data if the last filter decides to forward something */
+	if (ret > 0) {
+		ret = data;
+		*strm_off += ret;
+	}
  end:
 	DBG_TRACE_LEAVE(STRM_EV_TCP_ANA|STRM_EV_FLT_ANA, s);
 	return ret;