MINOR: connection: add sample fetch "fc_rcvd_proxy"

fc_rcvd_proxy : boolean
  Returns true if the client initiated the connection with a PROXY protocol
  header.

A flag is added on the struct connection if a PROXY header is successfully
parsed.

doc/configuration.txt

@@ -13149,6 +13149,10 @@ dst_port : integer
   a same server, or to pass the destination port information to a server using
   an HTTP header.
 
+fc_rcvd_proxy : boolean
+  Returns true if the client initiated the connection with a PROXY protocol
+  header.
+
 fc_rtt(<unit>) : integer
   Returns the Round Trip Time (RTT) measured by the kernel for the client
   connection. <unit> is facultative, by default the unit is milliseconds. <unit>

include/types/connection.h

@@ -127,7 +127,10 @@ enum {
 	/* This connection may not be shared between clients */
 	CO_FL_PRIVATE       = 0x10000000,
 
-	/* unused : 0x20000000, 0x40000000 */
+	/* This flag is used to know that a PROXY protocol header was sent by the client */
+	CO_FL_RCVD_PROXY    = 0x20000000,
+
+	/* unused : 0x40000000 */
 
 	/* This last flag indicates that the transport layer is used (for instance
 	 * by logs) and must not be cleared yet. The last call to conn_xprt_close()

src/connection.c

@@ -21,6 +21,7 @@
 #include <proto/frontend.h>
 #include <proto/proto_tcp.h>
 #include <proto/stream_interface.h>
+#include <proto/sample.h>
 
 #ifdef USE_OPENSSL
 #include <proto/ssl_sock.h>
@@ -603,6 +604,7 @@ int conn_recv_proxy(struct connection *conn, int flag)
 	} while (0);
 
 	conn->flags &= ~flag;
+	conn->flags |= CO_FL_RCVD_PROXY;
 	return 1;
 
  missing:
@@ -1040,3 +1042,41 @@ int make_proxy_line_v2(char *buf, int buf_len, struct server *srv, struct connec
 
 	return ret;
 }
+
+/* fetch if the received connection used a PROXY protocol header */
+int smp_fetch_fc_rcvd_proxy(const struct arg *args, struct sample *smp, const char *kw, void *private)
+{
+	struct connection *conn;
+
+	conn = objt_conn(smp->sess->origin);
+	if (!conn)
+		return 0;
+
+	if (!(conn->flags & CO_FL_CONNECTED)) {
+		smp->flags |= SMP_F_MAY_CHANGE;
+		return 0;
+	}
+
+	smp->flags = 0;
+	smp->data.type = SMP_T_BOOL;
+	smp->data.u.sint = (conn->flags & CO_FL_RCVD_PROXY) ? 1 : 0;
+
+	return 1;
+}
+
+/* Note: must not be declared <const> as its list will be overwritten.
+ * Note: fetches that may return multiple types must be declared as the lowest
+ * common denominator, the type that can be casted into all other ones. For
+ * instance v4/v6 must be declared v4.
+ */
+static struct sample_fetch_kw_list sample_fetch_keywords = {ILH, {
+	{ "fc_rcvd_proxy", smp_fetch_fc_rcvd_proxy, 0, NULL, SMP_T_BOOL, SMP_USE_L4CLI },
+	{ /* END */ },
+}};
+
+
+__attribute__((constructor))
+static void __connection_init(void)
+{
+	sample_register_fetches(&sample_fetch_keywords);
+}