src/patches/dnsmasq/0018-Make-caching-work-for-CNAMEs-pointing-to-A-AAAA-reco.patch

   1 From cbc652423403e3cef00e00240f6beef713142246 Mon Sep 17 00:00:00 2001
   2 From: Simon Kelley <simon@thekelleys.org.uk>
   3 Date: Sun, 21 Dec 2014 21:21:53 +0000
   4 Subject: [PATCH 18/98] Make caching work for CNAMEs pointing to A/AAAA records
   5  shadowed in /etc/hosts
   6
   7 If the answer to an upstream query is a CNAME which points to an
   8 A/AAAA record which also exists in /etc/hosts and friends, then
   9 caching is suppressed, to avoid inconsistent answers. This is
  10 now modified to allow caching when the upstream and local A/AAAA
  11 records have the same value.
  12 ---
  13  src/cache.c | 34 +++++++++++++++++++++++++---------
  14  1 file changed, 25 insertions(+), 9 deletions(-)
  15
  16 diff --git a/src/cache.c b/src/cache.c
  17 index f9e1d31e8c99..ff1ca6f1c352 100644
  18 --- a/src/cache.c
  19 +++ b/src/cache.c
  20 @@ -322,7 +322,7 @@ static int is_expired(time_t now, struct crec *crecp)
  21    return 1;
  22  }
  23
  24 -static int cache_scan_free(char *name, struct all_addr *addr, time_t now, unsigned short flags)
  25 +static struct crec *cache_scan_free(char *name, struct all_addr *addr, time_t now, unsigned short flags)
  26  {
  27    /* Scan and remove old entries.
  28       If (flags & F_FORWARD) then remove any forward entries for name and any expired
  29 @@ -331,8 +331,8 @@ static int cache_scan_free(char *name, struct all_addr *addr, time_t now, unsign
  30       entries in the whole cache.
  31       If (flags == 0) remove any expired entries in the whole cache.
  32
  33 -     In the flags & F_FORWARD case, the return code is valid, and returns zero if the
  34 -     name exists in the cache as a HOSTS or DHCP entry (these are never deleted)
  35 +     In the flags & F_FORWARD case, the return code is valid, and returns a non-NULL pointer
  36 +     to a cache entry if the name exists in the cache as a HOSTS or DHCP entry (these are never deleted)
  37
  38       We take advantage of the fact that hash chains have stuff in the order <reverse>,<other>,<immortal>
  39       so that when we hit an entry which isn't reverse and is immortal, we're done. */
  40 @@ -361,7 +361,7 @@ static int cache_scan_free(char *name, struct all_addr *addr, time_t now, unsign
  41                   (((crecp->flags | flags) & F_CNAME) && !(crecp->flags & (F_DNSKEY | F_DS))))
  42                 {
  43                   if (crecp->flags & (F_HOSTS | F_DHCP | F_CONFIG))
  44 -                   return 0;
  45 +                   return crecp;
  46                   *up = crecp->hash_next;
  47                   cache_unlink(crecp);
  48                   cache_free(crecp);
  49 @@ -378,7 +378,7 @@ static int cache_scan_free(char *name, struct all_addr *addr, time_t now, unsign
  50                    crecp->addr.sig.type_covered == addr->addr.dnssec.type))
  51                 {
  52                   if (crecp->flags & F_CONFIG)
  53 -                   return 0;
  54 +                   return crecp;
  55                   *up = crecp->hash_next;
  56                   cache_unlink(crecp);
  57                   cache_free(crecp);
  58 @@ -423,7 +423,7 @@ static int cache_scan_free(char *name, struct all_addr *addr, time_t now, unsign
  59             up = &crecp->hash_next;
  60      }
  61
  62 -  return 1;
  63 +  return NULL;
  64  }
  65
  66  /* Note: The normal calling sequence is
  67 @@ -471,10 +471,26 @@ struct crec *cache_insert(char *name, struct all_addr *addr,
  68      return NULL;
  69
  70    /* First remove any expired entries and entries for the name/address we
  71 -     are currently inserting. Fail if we attempt to delete a name from
  72 -     /etc/hosts or DHCP. */
  73 -  if (!cache_scan_free(name, addr, now, flags))
  74 +     are currently inserting. */
  75 +  if ((new = cache_scan_free(name, addr, now, flags)))
  76      {
  77 +      /* We're trying to insert a record over one from
  78 +        /etc/hosts or DHCP, or other config. If the
  79 +        existing record is for an A or AAAA and
  80 +        the record we're trying to insert is the same,
  81 +        just drop the insert, but don't error the whole process. */
  82 +      if ((flags & (F_IPV4 | F_IPV6)) && (flags & F_FORWARD))
  83 +       {
  84 +         if ((flags & F_IPV4) && (new->flags & F_IPV4) &&
  85 +             new->addr.addr.addr.addr4.s_addr == addr->addr.addr4.s_addr)
  86 +           return new;
  87 +#ifdef HAVE_IPV6
  88 +         else if ((flags & F_IPV6) && (new->flags & F_IPV6) &&
  89 +                  IN6_ARE_ADDR_EQUAL(&new->addr.addr.addr.addr6, &addr->addr.addr6))
  90 +           return new;
  91 +#endif
  92 +       }
  93 +
  94        insert_error = 1;
  95        return NULL;
  96      }
  97 --
  98 2.1.0
  99