app_rpt.c: Fix truncated link list in RPT_LINK

[mkmer]

Fixes #469 - processing received link list text message was limited to 512 characters. Expanded to MAXLINKLIST.

[InterLinked1]

It seems like tmp is mutable since we already have a copy of it (I haven't fully verified though)
Instead of the existing code, maybe we should replace with strsep for the first 3 strings and just use sscanf for the numbers? That way we can fix the issue more robustly as opposed to making a TODO?

[mkmer]

I don't disagree we should fix this, but in the interest of keeping this PR pointed at the actual issue maybe do it in a new PR? I'm thinking there would be a "general" fix up sscanf buffer over potentials everywhere, and hopefully the same way.
As for scanf, would %299s protect us with a lighter touch?

[mkmer]

Maybe something like this....

#define SIZE = 300
char format[20];
char one[SIZE], two[SIZE], three[SIZE]
sprintf(format,"%%%ds %%%ds %%%ds",SIZE-1,SIZE-1,SIZE-1);
sscanf(s, format, one, two, three);

[mkmer]

I general, this "fixes" the issue as seen. The questions that remain for a future PR (in my mind anyway):

• What is the max string we can receive from a text message - the initial call is a malloc, copy to pass str in.
• What is the max string a channel variable can accept? (Is it 5120 and that's why this value was chosen?) - appears that it can be any size? https://github.com/asterisk/asterisk/blob/32e6a309525cfd28133124cbe9e8c97fe9c90c52/utils/extconf.c#L2454-L2468
• Do we need to copy it in the routine, as it's malloc, copied, and freed around the call to either routine

  app_rpt/apps/app_rpt.c

  Lines 4407 to 4413 in e957e50

  	} else if (f->frametype == AST_FRAME_TEXT) {
  	char *tstr = ast_malloc(f->datalen + 1);
  	if (tstr) {
  	memcpy(tstr, f->data.ptr, f->datalen);
  	tstr[f->datalen] = 0;
  	handle_link_data(myrpt, l, tstr);
  	ast_free(tstr);

• Should l->linklist be a fixed value or be sized to the data (this may not be nice as we would malloc/free for every message received to resize it...)
• What is the "right" size for buf, or should it be malloc based on the size of the links when we build it (also depending on max channel variable size)? It could be VERY undersized if every l->linklist is MAXLINKLIST or even half.

  app_rpt/apps/app_rpt/rpt_link.c

  Line 526 in e957e50

  char buf[MAXLINKLIST], obuf[MAXLINKLIST + 20], *strs[MAXLINKLIST];