MINOR: proxy: Add fe_name/be_name fetchers next to existing fe_id/be_id

These 2 patches add ability to fetch frontend/backend name in your
logic, so they can be used later to make routing decisions (fe_name) or
taking some actions based on backend which responded to request (be_name).
In our case we needed a fetcher to be able to extract information we
needed from frontend name.

doc/configuration.txt

@@ -13089,6 +13089,10 @@ be_id : integer
   Returns an integer containing the current backend's id. It can be used in
   frontends with responses to check which backend processed the request.
 
+be_name : string
+  Returns a string containing the current backend's name. It can be used in
+  frontends with responses to check which backend processed the request.
+
 dst : ip
   This is the destination IPv4 address of the connection on the client side,
   which is the address the client connected to. It can be useful when running
@@ -13181,6 +13185,11 @@ fe_id : integer
   backends to check from which backend it was called, or to stick all users
   coming via a same frontend to the same server.
 
+fe_name : string
+  Returns a string containing the current frontend's name. It can be used in
+  backends to check from which frontend it was called, or to stick all users
+  coming via a same frontend to the same server.
+
 sc_bytes_in_rate(<ctr>[,<table>]) : integer
 sc0_bytes_in_rate([<table>]) : integer
 sc1_bytes_in_rate([<table>]) : integer

src/backend.c

@@ -1681,6 +1681,24 @@ smp_fetch_be_id(const struct arg *args, struct sample *smp, const char *kw, void
 	return 1;
 }
 
+/* set string to the name of the backend */
+static int
+smp_fetch_be_name(const struct arg *args, struct sample *smp, const char *kw, void *private)
+{
+	if (!smp->strm)
+		return 0;
+
+	smp->data.u.str.str = (char *)smp->strm->be->id;
+	if (!smp->data.u.str.str)
+	        return 0;
+
+	smp->data.type = SMP_T_STR;
+	smp->flags = SMP_F_CONST;
+	smp->data.u.str.len = strlen(smp->data.u.str.str);
+
+	return 1;
+}
+
 /* set temp integer to the id of the server */
 static int
 smp_fetch_srv_id(const struct arg *args, struct sample *smp, const char *kw, void *private)
@@ -1803,6 +1821,7 @@ static struct sample_fetch_kw_list smp_kws = {ILH, {
 	{ "avg_queue",     smp_fetch_avg_queue_size, ARG1(1,BE),  NULL, SMP_T_SINT, SMP_USE_INTRN, },
 	{ "be_conn",       smp_fetch_be_conn,        ARG1(1,BE),  NULL, SMP_T_SINT, SMP_USE_INTRN, },
 	{ "be_id",         smp_fetch_be_id,          0,           NULL, SMP_T_SINT, SMP_USE_BKEND, },
+	{ "be_name",       smp_fetch_be_name,        0,           NULL, SMP_T_STR,  SMP_USE_BKEND, },
 	{ "be_sess_rate",  smp_fetch_be_sess_rate,   ARG1(1,BE),  NULL, SMP_T_SINT, SMP_USE_INTRN, },
 	{ "connslots",     smp_fetch_connslots,      ARG1(1,BE),  NULL, SMP_T_SINT, SMP_USE_INTRN, },
 	{ "nbsrv",         smp_fetch_nbsrv,          ARG1(1,BE),  NULL, SMP_T_SINT, SMP_USE_INTRN, },

src/frontend.c

@@ -167,6 +167,20 @@ smp_fetch_fe_id(const struct arg *args, struct sample *smp, const char *kw, void
 	return 1;
 }
 
+/* set string to the name of the frontend */
+static int
+smp_fetch_fe_name(const struct arg *args, struct sample *smp, const char *kw, void *private)
+{
+	smp->data.u.str.str = (char *)smp->sess->fe->id;
+	if (!smp->data.u.str.str)
+		return 0;
+
+	smp->data.type = SMP_T_STR;
+	smp->flags = SMP_F_CONST;
+	smp->data.u.str.len = strlen(smp->data.u.str.str);
+	return 1;
+}
+
 /* set temp integer to the number of HTTP requests per second reaching the frontend.
  * Accepts exactly 1 argument. Argument is a frontend, other types will cause
  * an undefined behaviour.
@@ -213,6 +227,7 @@ smp_fetch_fe_conn(const struct arg *args, struct sample *smp, const char *kw, vo
 static struct sample_fetch_kw_list smp_kws = {ILH, {
 	{ "fe_conn",      smp_fetch_fe_conn,      ARG1(1,FE), NULL, SMP_T_SINT, SMP_USE_INTRN, },
 	{ "fe_id",        smp_fetch_fe_id,        0,          NULL, SMP_T_SINT, SMP_USE_FTEND, },
+	{ "fe_name",      smp_fetch_fe_name,      0,          NULL, SMP_T_STR,  SMP_USE_FTEND, },
 	{ "fe_req_rate",  smp_fetch_fe_req_rate,  ARG1(1,FE), NULL, SMP_T_SINT, SMP_USE_INTRN, },
 	{ "fe_sess_rate", smp_fetch_fe_sess_rate, ARG1(1,FE), NULL, SMP_T_SINT, SMP_USE_INTRN, },
 	{ /* END */ },