MINOR: check: implement check-pool-conn-name srv keyword

This commit is a direct follow-up of the previous one. It defines a new
server keyword check-pool-conn-name. It is used as the default value for
the name parameter of idle connection hash generation.

Its behavior is similar to server keyword pool-conn-name, but reserved
for checks reuse. If check-pool-conn-name is set, it is used in priority
to match a connection for reuse. If unset, a fallback is performed on
check-sni.

doc/configuration.txt

@@ -18218,6 +18218,8 @@ check-reuse-pool
   This option is automatically enabled for servers acting as passive reverse
   HTTP gateway, as for those servers connect is only supported through reuse.
 
+  See also: "check-pool-conn-name"
+
 check-send-proxy
   May be used in the following contexts: tcp, http
 
@@ -18236,6 +18238,16 @@ check-alpn <protocols>
   a comma-delimited list of protocol names, for instance: "http/1.1,http/1.0"
   (without quotes). If it is not set, the server ALPN is used.
 
+check-pool-conn-name <name>
+  May be used in the following contexts: tcp, http
+
+  When connection reuse is performed for checks, uses <name> if set as a
+  connection identifier to match a corresponding connection in the pool. This
+  serves as the equivalent to the "pool-conn-name" server keyword. "check-sni"
+  will also be used as a fallback if the current option is not used.
+
+  See also: "check-reuse-pool"
+
 check-proto <name>
   May be used in the following contexts: tcp, http
 

include/haproxy/check-t.h

@@ -188,6 +188,7 @@ struct check {
 	char **envp;				/* the environment to use if running a process-based check */
 	struct pid_list *curpid;		/* entry in pid_list used for current process-based test, or -1 if not in test */
 	struct sockaddr_storage addr;   	/* the address to check */
+	char *pool_conn_name;                   /* conn name used on reuse */
 	char *sni;				/* Server name */
 	char *alpn_str;                         /* ALPN to use for checks */
 	int alpn_len;                           /* ALPN string length */

src/check.c

@@ -1572,6 +1572,8 @@ void free_check(struct check *check)
 		ha_free(&check->tcpcheck_rules);
 	}
 
+	ha_free(&check->pool_conn_name);
+
 	task_destroy(check->task);
 
 	check_release_buf(check, &check->bi);
@@ -2362,6 +2364,34 @@ static int srv_parse_no_check_send_proxy(char **args, int *cur_arg, struct proxy
 	return 0;
 }
 
+/* parse the "check-pool-conn-name" server keyword */
+static int srv_parse_check_pool_conn_name(char **args, int *cur_arg,
+                                          struct proxy *px,
+                                          struct server *newsrv, char **err)
+{
+	int err_code = 0;
+
+	if (!*args[*cur_arg + 1]) {
+		memprintf(err, "'%s' : missing value", args[*cur_arg]);
+		goto error;
+	}
+
+	ha_free(&newsrv->check.pool_conn_name);
+	newsrv->check.pool_conn_name = strdup(args[*cur_arg + 1]);
+	if (!newsrv->check.pool_conn_name) {
+		memprintf(err, "'%s' : out of memory", args[*cur_arg]);
+		return ERR_ALERT | ERR_FATAL;
+	}
+
+  out:
+	return err_code;
+
+  error:
+	err_code |= ERR_ALERT | ERR_FATAL;
+	goto out;
+}
+
+
 /* parse the "check-proto" server keyword */
 static int srv_parse_check_proto(char **args, int *cur_arg,
 				 struct proxy *px, struct server *newsrv, char **err)
@@ -2662,6 +2692,7 @@ static struct srv_kw_list srv_kws = { "CHK", { }, {
 	{ "agent-port",          srv_parse_agent_port,          1,  1,  1 }, /* Set the TCP port used for agent checks. */
 	{ "agent-send",          srv_parse_agent_send,          1,  1,  1 }, /* Set string to send to agent. */
 	{ "check",               srv_parse_check,               0,  1,  1 }, /* Enable health checks */
+	{ "check-pool-conn-name", srv_parse_check_pool_conn_name, 1, 1, 1 }, /* */
 	{ "check-proto",         srv_parse_check_proto,         1,  1,  1 }, /* Set the mux protocol for health checks  */
 	{ "check-reuse-pool",    srv_parse_check_reuse_pool,    0,  1,  1 }, /* Allows to reuse idle connections for checks */
 	{ "check-send-proxy",    srv_parse_check_send_proxy,    0,  1,  1 }, /* Enable PROXY protocol for health checks */

src/server.c

@@ -2854,6 +2854,8 @@ void srv_settings_cpy(struct server *srv, const struct server *src, int srv_tmpl
 	srv->check.alpn_len           = src->check.alpn_len;
 	if (!(srv->flags & SRV_F_RHTTP))
 		srv->check.reuse_pool = src->check.reuse_pool;
+	if (src->check.pool_conn_name)
+		srv->check.pool_conn_name = strdup(src->check.pool_conn_name);
 	/* Note: 'flags' field has potentially been already initialized. */
 	srv->flags                   |= src->flags;
 	srv->do_check                 = src->do_check;

src/tcpcheck.c

@@ -1272,7 +1272,9 @@ enum tcpcheck_eval_ret tcpcheck_eval_connect(struct check *check, struct tcpchec
 
 		TRACE_DEVEL("trying connection reuse for check", CHK_EV_TCPCHK_CONN, check);
 
-		if (connect->sni)
+		if (check->pool_conn_name)
+			pool_conn_name = ist(check->pool_conn_name);
+		else if (connect->sni)
 			pool_conn_name = ist(connect->sni);
 		else if ((connect->options & TCPCHK_OPT_DEFAULT_CONNECT) && check->sni)
 			pool_conn_name = ist(check->sni);