package/network/services/dnsmasq/patches/250-Fix-infinite-retries-in-strict-order-mode.patch

   1 From ef3d137a646fa8309e1ff5184e3e145eef40cc4d Mon Sep 17 00:00:00 2001
   2 From: Simon Kelley <simon@thekelleys.org.uk>
   3 Date: Tue, 5 Dec 2017 22:37:29 +0000
   4 Subject: [PATCH] Fix infinite retries in strict-order mode.
   5
   6  If all configured dns servers return refused in
   7  response to a query; dnsmasq will end up in an infinite loop
   8  retransmitting the dns query resulting into high CPU load.
   9  Problem is caused by the dns refuse retransmission logic which does
  10  not check for the end of a dns server list iteration in strict mode.
  11  Having one configured dns server returning a refused reply easily
  12  triggers this problem in strict order mode. This was introduced in
  13  9396752c115b3ab733fa476b30da73237e12e7ba
  14
  15  Thanks to Hans Dedecker <dedeckeh@gmail.com> for spotting this
  16  and the initial patch.
  17 ---
  18  src/forward.c | 14 ++++++++++++--
  19  1 file changed, 12 insertions(+), 2 deletions(-)
  20
  21 --- a/src/forward.c
  22 +++ b/src/forward.c
  23 @@ -797,10 +797,20 @@ void reply_query(int fd, int family, tim
  24        unsigned char *pheader;
  25        size_t plen;
  26        int is_sign;
  27 -
  28 +
  29 +      /* In strict order mode, there must be a server later in the chain
  30 +        left to send to, otherwise without the forwardall mechanism,
  31 +        code further on will cycle around the list forwever if they
  32 +        all return REFUSED. Note that server is always non-NULL before
  33 +        this executes. */
  34 +      if (option_bool(OPT_ORDER))
  35 +       for (server = forward->sentto->next; server; server = server->next)
  36 +         if (!(server->flags & (SERV_LITERAL_ADDRESS | SERV_HAS_DOMAIN | SERV_FOR_NODOTS | SERV_NO_ADDR | SERV_LOOP)))
  37 +           break;
  38 +
  39        /* recreate query from reply */
  40        pheader = find_pseudoheader(header, (size_t)n, &plen, NULL, &is_sign, NULL);
  41 -      if (!is_sign)
  42 +      if (!is_sign && server)
  43         {
  44           header->ancount = htons(0);
  45           header->nscount = htons(0);