MEDIUM: counters: factor out smp_fetch_sc*_gpc0_rate

smp_fetch_sc0_gpc0, smp_fetch_sc1_gpc0, smp_fetch_sc2_gpc0,
smp_fetch_src_gpc0 and smp_fetch_gpc0 were merged into a single
function which relies on the fetch name to decide what to return.
diff --git a/src/session.c b/src/session.c
index ba692f0..af6f3eb 100644
--- a/src/session.c
+++ b/src/session.c
@@ -2646,77 +2646,33 @@
 	return 1;
 }
 
-/* set temp integer to the General Purpose Counter 0's event rate in the stksess entry <ts> */
+/* set <smp> to the General Purpose Counter 0's event rate from the session's
+ * tracked frontend counters or from the src.
+ * Supports being called as "sc[0-9]_gpc0_rate" or "src_gpc0_rate" only.
+ * Value zero is returned if the key is new.
+ */
 static int
-smp_fetch_gpc0_rate(struct stktable *table, struct sample *smp, struct stksess *ts)
+smp_fetch_sc_gpc0_rate(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
+                       const struct arg *args, struct sample *smp, const char *kw)
 {
+	struct stkctr *stkctr = smp_fetch_sc_stkctr(l4, args, kw);
+
+	if (!stkctr)
+		return 0;
+
 	smp->flags = SMP_F_VOL_TEST;
 	smp->type = SMP_T_UINT;
 	smp->data.uint = 0;
-	if (ts != NULL) {
-		void *ptr = stktable_data_ptr(table, ts, STKTABLE_DT_GPC0_RATE);
+	if (stkctr->entry != NULL) {
+		void *ptr = stktable_data_ptr(stkctr->table, stkctr->entry, STKTABLE_DT_GPC0_RATE);
 		if (!ptr)
 			return 0; /* parameter not stored */
 		smp->data.uint = read_freq_ctr_period(&stktable_data_cast(ptr, gpc0_rate),
-					       table->data_arg[STKTABLE_DT_GPC0_RATE].u);
+		                                      stkctr->table->data_arg[STKTABLE_DT_GPC0_RATE].u);
 	}
 	return 1;
 }
 
-/* set temp integer to the General Purpose Counter 0's event rate from the
- * session's tracked frontend counters.
- */
-static int
-smp_fetch_sc0_gpc0_rate(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
-                       const struct arg *args, struct sample *smp, const char *kw)
-{
-	if (!l4->stkctr[0].entry)
-		return 0;
-	return smp_fetch_gpc0_rate(l4->stkctr[0].table, smp, l4->stkctr[0].entry);
-}
-
-/* set temp integer to the General Purpose Counter 0's event rate from the
- * session's tracked backend counters.
- */
-static int
-smp_fetch_sc1_gpc0_rate(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
-                       const struct arg *args, struct sample *smp, const char *kw)
-{
-	if (!l4->stkctr[1].entry)
-		return 0;
-	return smp_fetch_gpc0_rate(l4->stkctr[1].table, smp, l4->stkctr[1].entry);
-}
-
-/* set temp integer to the General Purpose Counter 0's event rate from the
- * session's tracked backend counters.
- */
-static int
-smp_fetch_sc2_gpc0_rate(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
-                       const struct arg *args, struct sample *smp, const char *kw)
-{
-	if (!l4->stkctr[2].entry)
-		return 0;
-	return smp_fetch_gpc0_rate(l4->stkctr[2].table, smp, l4->stkctr[2].entry);
-}
-
-/* set temp integer to the General Purpose Counter 0's event rate from the
- * session's source address in the table pointed to by expr.
- * Accepts exactly 1 argument of type table.
- */
-static int
-smp_fetch_src_gpc0_rate(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
-                       const struct arg *args, struct sample *smp, const char *kw)
-{
-	struct stktable_key *key;
-
-	key = addr_to_stktable_key(&l4->si[0].conn->addr.from);
-	if (!key)
-		return 0;
-
-	px = args->data.prx;
-	return smp_fetch_gpc0_rate(&px->table, smp, stktable_lookup_key(&px->table, key));
-}
-
 /* Increment the General Purpose Counter 0 value in the stksess entry <ts> and
  * return it into temp integer.
  */
@@ -3916,7 +3872,7 @@
 	{ "sc0_conn_cur",       smp_fetch_sc0_conn_cur,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc0_conn_rate",      smp_fetch_sc0_conn_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc0_get_gpc0",       smp_fetch_sc_get_gpc0,        0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
-	{ "sc0_gpc0_rate",      smp_fetch_sc0_gpc0_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
+	{ "sc0_gpc0_rate",      smp_fetch_sc_gpc0_rate,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc0_http_err_cnt",   smp_fetch_sc0_http_err_cnt,   0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc0_http_err_rate",  smp_fetch_sc0_http_err_rate,  0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc0_http_req_cnt",   smp_fetch_sc0_http_req_cnt,   0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
@@ -3935,7 +3891,7 @@
 	{ "sc1_conn_cur",       smp_fetch_sc1_conn_cur,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc1_conn_rate",      smp_fetch_sc1_conn_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc1_get_gpc0",       smp_fetch_sc_get_gpc0,        0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
-	{ "sc1_gpc0_rate",      smp_fetch_sc1_gpc0_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
+	{ "sc1_gpc0_rate",      smp_fetch_sc_gpc0_rate,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc1_http_err_cnt",   smp_fetch_sc1_http_err_cnt,   0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc1_http_err_rate",  smp_fetch_sc1_http_err_rate,  0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc1_http_req_cnt",   smp_fetch_sc1_http_req_cnt,   0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
@@ -3954,7 +3910,7 @@
 	{ "sc2_conn_cur",       smp_fetch_sc2_conn_cur,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc2_conn_rate",      smp_fetch_sc2_conn_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc2_get_gpc0",       smp_fetch_sc_get_gpc0,        0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
-	{ "sc2_gpc0_rate",      smp_fetch_sc2_gpc0_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
+	{ "sc2_gpc0_rate",      smp_fetch_sc_gpc0_rate,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc2_http_err_cnt",   smp_fetch_sc2_http_err_cnt,   0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc2_http_err_rate",  smp_fetch_sc2_http_err_rate,  0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc2_http_req_cnt",   smp_fetch_sc2_http_req_cnt,   0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
@@ -3973,7 +3929,7 @@
 	{ "src_conn_cur",       smp_fetch_src_conn_cur,       ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "src_conn_rate",      smp_fetch_src_conn_rate,      ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "src_get_gpc0",       smp_fetch_sc_get_gpc0,        ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },
-	{ "src_gpc0_rate",      smp_fetch_src_gpc0_rate,      ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },
+	{ "src_gpc0_rate",      smp_fetch_sc_gpc0_rate,       ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "src_http_err_cnt",   smp_fetch_src_http_err_cnt,   ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "src_http_err_rate",  smp_fetch_src_http_err_rate,  ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "src_http_req_cnt",   smp_fetch_src_http_req_cnt,   ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },