From: Andres Freund <andres@anarazel.de>
Date: Wed, 20 Sep 2017 08:12:32 +0000 (-0700)
Subject: Add ability to force libpq to negotiate a specific version of the protocol.
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=36bfaf50ff0bfac9eb45956912bb149093bbcd37;p=users%2Fandresfreund%2Fpostgres.git

Add ability to force libpq to negotiate a specific version of the protocol.

Author: Andres Freund
Discussion: https://postgr.es/m/20170918095303.g766pdnvviqlewph@alap3.anarazel.de
---

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 5f79803607..b4d57d9d45 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -323,6 +323,10 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
 		"Target-Session-Attrs", "", 11, /* sizeof("read-write") = 11 */
 	offsetof(struct pg_conn, target_session_attrs)},
 
+	{"forced_protocol_version", "PGFORCEPROTOCOLVERSION", NULL, NULL,
+	 "Forced-version", "D", sizeof("Forced-version"),
+	offsetof(struct pg_conn, forced_protocol_version)},
+
 	/* Terminating entry --- MUST BE LAST */
 	{NULL, NULL, NULL, NULL,
 	NULL, NULL, 0}
@@ -1803,7 +1807,14 @@ connectDBStart(PGconn *conn)
 	 */
 	conn->whichhost = 0;
 	conn->addr_cur = conn->connhost[0].addrlist;
-	conn->pversion = PG_PROTOCOL(3, 0);
+	if (conn->forced_protocol_version != NULL)
+	{
+		conn->pversion = atoi(conn->forced_protocol_version);
+	}
+	else
+	{
+		conn->pversion = PG_PROTOCOL(3, 0);
+	}
 	conn->send_appname = true;
 	conn->status = CONNECTION_NEEDED;
 
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 42913604e3..7bfc09ec71 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -364,6 +364,9 @@ struct pg_conn
 	/* Type of connection to make.  Possible values: any, read-write. */
 	char	   *target_session_attrs;
 
+	char	   *forced_protocol_version; /* for testing: force protocol to a
+										  * specific version */
+
 	/* Optional file to write trace info to */
 	FILE	   *Pfdebug;