Routing table name lookup failure

[Andrew Kraslavsky]

When I tried to send the message below last week I got a warning that it contained suspicious content (?) and, since it has not yet shown up on the list, I'm trying it again.

----------------------------------------
> From: andykras at hotmail.com
> To: libnl at lists.infradead.org
> Subject: Routing table name lookup failure
> Date: Thu, 29 Sep 2011 17:52:46 -0700
>
>
> Hello,
>
> I am using:
>
> libnl version 3.0
> Linux kernel version 2.6.35.12
>
> I have encountered a problem where, if I call rtnl_route_read_table_names, subsequent calls to rtnl_route_table2str return the ID as a hexadecimal string (e.g. "0xFE") instead of the name (e.g. "main") of the table. Sometimes, after calling rtnl_route_read_table_names my program will crash due to memory corruption. Please note that /etc/iproute2/rt_tables has not been modified.
>
> Here's the call sequence:
>
> if( rtnl_route_read_table_names( "/etc/iproute2/rt_tables" ) == 0 ){
>
>
>
>     char buf[32];
>
>
>
>
>
>     printf( "Name: %s\n",  rtnl_route_table2str( 254, buf, sizeof( buf ) ) );
>
> }
>
> The print statement should show "mainline" but instead shows "0xFE".
>
> I think I have tracked the problem down to __trans_list_clear, which is called by rtnl_route_read_table_names to flush any existing table_names list entries before repopulating it based on the contents of the specified file.
>
> in __trans_list_clear, all entries are freed but the list head's previous and next pointers are not reset so the list continues to hold references to freed memory.
>
> I created and applied the patch listed below to address this and it seems to do the trick.  Please take a look at it and see if it will be of use.
>
> ==== //tps/libnl/3.0/mainline/src/lib/utils.c#3 .../src/lib/utils.c ====
>
> @@ -854,16 +854,17 @@
>
>  void __trans_list_clear(struct nl_list_head *head)
>
>  {
>
>         struct trans_list *tl, *next;
>
>
>
>         nl_list_for_each_entry_safe(tl, next, head, list) {
>
>                 free(tl->a);
>
>                 free(tl);
>
>         }
>
> +       nl_init_list_head(head);
>
>  }
>
> Thank you,
>
> - Andrew
>
>