From: Tim Duesterhus <tim@bastelstu.be>
Date: Thu, 3 Jan 2019 23:11:59 +0000 (+0100)
Subject: BUG/MINOR: stick_table: Prevent conn_cur from underflowing
X-Git-Tag: v2.0-dev1~201
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8b87c01c4d59247d9fb51a38cd12d5d94324b6a4;p=thirdparty%2Fhaproxy.git

BUG/MINOR: stick_table: Prevent conn_cur from underflowing

When using the peers feature a race condition could prevent
a connection from being properly counted. When this connection
exits it is being "uncounted" nonetheless, leading to a possible
underflow (-1) of the conn_curr stick table entry in the following
scenario :

  - Connect to peer A     (A=1, B=0)
  - Peer A sends 1 to B   (A=1, B=1)
  - Kill connection to A  (A=0, B=1)
  - Connect to peer B     (A=0, B=2)
  - Peer A sends 0 to B   (A=0, B=0)
  - Peer B sends 0/2 to A (A=?, B=0)
  - Kill connection to B  (A=?, B=-1)
  - Peer B sends -1 to A  (A=-1, B=-1)

This fix may be backported to all supported branches.
---

diff --git a/include/proto/session.h b/include/proto/session.h
index d54e9454b5..0b7d08d995 100644
--- a/include/proto/session.h
+++ b/include/proto/session.h
@@ -62,7 +62,8 @@ static inline void session_store_counters(struct session *sess)
 		if (ptr) {
 			HA_RWLOCK_WRLOCK(STK_SESS_LOCK, &ts->lock);
 
-			stktable_data_cast(ptr, conn_cur)--;
+			if (stktable_data_cast(ptr, conn_cur) > 0)
+				stktable_data_cast(ptr, conn_cur)--;
 
 			HA_RWLOCK_WRUNLOCK(STK_SESS_LOCK, &ts->lock);
 
diff --git a/include/proto/stream.h b/include/proto/stream.h
index f448209770..a8c2992142 100644
--- a/include/proto/stream.h
+++ b/include/proto/stream.h
@@ -103,7 +103,8 @@ static inline void stream_store_counters(struct stream *s)
 		if (ptr) {
 			HA_RWLOCK_WRLOCK(STK_SESS_LOCK, &ts->lock);
 
-			stktable_data_cast(ptr, conn_cur)--;
+			if (stktable_data_cast(ptr, conn_cur) > 0)
+				stktable_data_cast(ptr, conn_cur)--;
 
 			HA_RWLOCK_WRUNLOCK(STK_SESS_LOCK, &ts->lock);
 
@@ -141,7 +142,8 @@ static inline void stream_stop_content_counters(struct stream *s)
 		if (ptr) {
 			HA_RWLOCK_WRLOCK(STK_SESS_LOCK, &ts->lock);
 
-			stktable_data_cast(ptr, conn_cur)--;
+			if (stktable_data_cast(ptr, conn_cur) > 0)
+				stktable_data_cast(ptr, conn_cur)--;
 
 			HA_RWLOCK_WRUNLOCK(STK_SESS_LOCK, &ts->lock);