MINOR: connection: report the major HTTP version from the MUX for logging (fc_http_major)

A new sample fetch function reports either 1 or 2 for the on-wire encoding,
to indicate if the request was received using the HTTP/1.x format or HTTP/2
format. Note that it reports the on-wire encoding, not the version presented
in the request header.

This will possibly have to evolve if it becomes necessary to report the
encoding on the server side as well.

doc/configuration.txt

@@ -13591,6 +13591,11 @@ dst_port : integer
   a same server, or to pass the destination port information to a server using
   an HTTP header.
 
+fc_http_major : integer
+  Reports the front connection's HTTP major version encoding, which may be 1
+  for HTTP/0.9 to HTTP/1.1 or 2 for HTTP/2. Note, this is based on the on-wire
+  encoding and not on the version present in the request header.
+
 fc_rcvd_proxy : boolean
   Returns true if the client initiated the connection with a PROXY protocol
   header.

src/connection.c

@@ -1077,6 +1077,19 @@ int make_proxy_line_v2(char *buf, int buf_len, struct server *srv, struct connec
 	return ret;
 }
 
+/* return the major HTTP version as 1 or 2 depending on how the request arrived
+ * before being processed.
+ */
+static int
+smp_fetch_fc_http_major(const struct arg *args, struct sample *smp, const char *kw, void *private)
+{
+	struct connection *conn = objt_conn(smp->sess->origin);
+
+	smp->data.type = SMP_T_SINT;
+	smp->data.u.sint = (conn && strcmp(conn_get_mux_name(conn), "H2") == 0) ? 2 : 1;
+	return 1;
+}
+
 /* 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)
 {
@@ -1104,6 +1117,7 @@ int smp_fetch_fc_rcvd_proxy(const struct arg *args, struct sample *smp, const ch
  * instance v4/v6 must be declared v4.
  */
 static struct sample_fetch_kw_list sample_fetch_keywords = {ILH, {
+	{ "fc_http_major", smp_fetch_fc_http_major, 0, NULL, SMP_T_SINT, SMP_USE_L4CLI },
 	{ "fc_rcvd_proxy", smp_fetch_fc_rcvd_proxy, 0, NULL, SMP_T_BOOL, SMP_USE_L4CLI },
 	{ /* END */ },
 }};