Commits on Aug 22, 2018

1. problem: 2nd key in bpf_map_get_next_key usage is the current one. …

   The 2nd key passed to bpf_map_get_next_key is the one that contains
   the current key in the iteration.
   
   If the map only contains a single key, after one call to
   bpf_map_get_next_key key is undefined and next_key is the first item.
   doing key = next_key and calling bpf_map_get_next_key ends the loop
   because there are no more keys and bpf_map_lookup_elem is never called
   with the first key.  I believe in maps containing more than one key this
   will just result in the first key being skipped.
   
   linux/samples/bpf/sampleip_user.c is one of the only uses of
   bpf_map_get_next_key I can find, and they do:
   
       key = 0, i = 0;
       while (bpf_map_get_next_key(fd, &key, &next_key) == 0) {
               bpf_map_lookup_elem(fd, &next_key, &value);
               counts[i].ip = next_key;
               counts[i++].count = value;
               key = next_key;
       }
   
   Note how bpf_map_lookup_elem is called with next_key, not key.
   
   To avoid having to change a ton of references to key, I just renamed key
   to prev_key and nextkey to key.

   

   JustinAzoff committed Aug 22, 2018
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