Fix overflow when using large number of GW per rule

Instead of fix-size internal buffer, user self-scaling buffers for handling/sorting the destinations/gateways in rules and carriers.
Fixes #1910

Cherry pick from e5991e1

modules/drouting/drouting.c

@@ -2405,12 +2405,27 @@ static int use_next_gw_w_part(struct sip_msg* msg,
 }
 
 
-#define DR_MAX_GWLIST	64
+#define resize_dr_sort_buffer( _buf, _old_size, _new_size, _error) \
+	do { \
+		if (_new_size > _old_size) { \
+			/* need a larger buffer */ \
+			_buf = (unsigned short*)pkg_realloc( _buf, \
+				_new_size *sizeof(unsigned short) ); \
+			if (_buf==NULL) { \
+				LM_ERR("no more pkg mem (needed  %ld)\n", \
+					_new_size*sizeof(unsigned short));\
+				_old_size = 0; \
+				goto _error;\
+			}\
+			_old_size = _new_size; \
+		} \
+	}while(0) \
 
 static int sort_rt_dst(pgw_list_t *pgwl, unsigned short size,
 		int weight, unsigned short *idx)
 {
-	unsigned short running_sum[DR_MAX_GWLIST];
+	static unsigned short *running_sum = NULL;
+	static unsigned short sum_buf_size = 0;
 	unsigned int i, first, weight_sum, rand_no;
 
 	/* populate the index array */
@@ -2421,6 +2436,7 @@ static int sort_rt_dst(pgw_list_t *pgwl, unsigned short size,
 		return 0;
 
 	while (size-first>1) {
+		resize_dr_sort_buffer( running_sum, sum_buf_size, size, err);
 		/* calculate the running sum */
 		for( i=first,weight_sum=0 ; i<size ; i++ ) {
 			weight_sum += pgwl[ idx[i] ].weight ;
@@ -2437,7 +2453,7 @@ static int sort_rt_dst(pgw_list_t *pgwl, unsigned short size,
 				if (running_sum[i]>rand_no) break;
 			if (i==size) {
 				LM_CRIT("bug in weight sort\n");
-				return -1;
+				goto err;
 			}
 		} else {
 			/* randomly select index */
@@ -2455,6 +2471,8 @@ static int sort_rt_dst(pgw_list_t *pgwl, unsigned short size,
 	}
 
 	return 0;
+err:
+	return -1;
 }
 
 
@@ -2603,8 +2621,10 @@ struct head_db * get_partition(const str *name) {
 static int do_routing(struct sip_msg* msg, dr_part_group_t * part_group,
 												int flags, gparam_t* whitelist)
 {
-	unsigned short dsts_idx[DR_MAX_GWLIST];
-	unsigned short carrier_idx[DR_MAX_GWLIST];
+	static unsigned short *dsts_idx = NULL;
+	static unsigned short dsts_idx_size = 0;
+	static unsigned short *carrier_idx = NULL;
+	static unsigned short carrier_idx_size = 0;
 	struct to_body  *from;
 	struct sip_uri  uri;
 	rt_info_t  *rt_info;
@@ -2885,6 +2905,7 @@ static int do_routing(struct sip_msg* msg, dr_part_group_t * part_group,
 	}
 
 	/* sort the destination elements in the rule */
+	resize_dr_sort_buffer( dsts_idx, dsts_idx_size, rt_info->pgwa_len, error2);
 	i = sort_rt_dst(rt_info->pgwl, rt_info->pgwa_len,
 			flags&DR_PARAM_USE_WEIGTH, dsts_idx);
 	if (i!=0) {
@@ -2928,6 +2949,8 @@ static int do_routing(struct sip_msg* msg, dr_part_group_t * part_group,
 				continue;
 
 			/* sort the gws of the carrier */
+			resize_dr_sort_buffer( carrier_idx, carrier_idx_size,
+				dst->dst.carrier->pgwa_len, skip);
 			j = sort_rt_dst(dst->dst.carrier->pgwl, dst->dst.carrier->pgwa_len,
 					dst->dst.carrier->flags&DR_CR_FLAG_WEIGHT, carrier_idx);
 			if (j!=0) {
@@ -2968,6 +2991,8 @@ static int do_routing(struct sip_msg* msg, dr_part_group_t * part_group,
 				}
 
 			}
+			skip:
+			;
 
 		} else {
 
@@ -3151,7 +3176,8 @@ static int do_routing(struct sip_msg* msg, dr_part_group_t * part_group,
 static int route2_carrier(struct sip_msg* msg, char* part_carrier,
 		char* gw_att_pv, char* carr_att_pv)
 {
-	unsigned short carrier_idx[DR_MAX_GWLIST];
+	static unsigned short *carrier_idx;
+	static unsigned short carrier_idx_size;
 	struct sip_uri  uri;
 	pgw_list_t *cdst;
 	pcr_t *cr;
@@ -3249,6 +3275,8 @@ static int route2_carrier(struct sip_msg* msg, char* part_carrier,
 		goto no_gws;
 
 	/* sort the gws of the carrier */
+	resize_dr_sort_buffer( carrier_idx, carrier_idx_size,
+			cr->pgwa_len, error);
 	j = sort_rt_dst( cr->pgwl, cr->pgwa_len, cr->flags&DR_CR_FLAG_WEIGHT,
 			carrier_idx);
 	if (j!=0) {