target/linux/generic/patches-4.9/611-netfilter_match_bypass_default_table.patch

   1 --- a/net/ipv4/netfilter/ip_tables.c
   2 +++ b/net/ipv4/netfilter/ip_tables.c
   3 @@ -254,6 +254,33 @@ struct ipt_entry *ipt_next_entry(const s
   4         return (void *)entry + entry->next_offset;
   5  }
   6
   7 +static bool
   8 +ipt_handle_default_rule(struct ipt_entry *e, unsigned int *verdict)
   9 +{
  10 +       struct xt_entry_target *t;
  11 +       struct xt_standard_target *st;
  12 +
  13 +       if (e->target_offset != sizeof(struct ipt_entry))
  14 +               return false;
  15 +
  16 +       if (!(e->ip.flags & IPT_F_NO_DEF_MATCH))
  17 +               return false;
  18 +
  19 +       t = ipt_get_target(e);
  20 +       if (t->u.kernel.target->target)
  21 +               return false;
  22 +
  23 +       st = (struct xt_standard_target *) t;
  24 +       if (st->verdict == XT_RETURN)
  25 +               return false;
  26 +
  27 +       if (st->verdict >= 0)
  28 +               return false;
  29 +
  30 +       *verdict = (unsigned)(-st->verdict) - 1;
  31 +       return true;
  32 +}
  33 +
  34  /* Returns one of the generic firewall policies, like NF_ACCEPT. */
  35  unsigned int
  36  ipt_do_table(struct sk_buff *skb,
  37 @@ -274,28 +301,8 @@ ipt_do_table(struct sk_buff *skb,
  38         unsigned int addend;
  39
  40         /* Initialization */
  41 -       stackidx = 0;
  42 -       ip = ip_hdr(skb);
  43 -       indev = state->in ? state->in->name : nulldevname;
  44 -       outdev = state->out ? state->out->name : nulldevname;
  45 -       /* We handle fragments by dealing with the first fragment as
  46 -        * if it was a normal packet.  All other fragments are treated
  47 -        * normally, except that they will NEVER match rules that ask
  48 -        * things we don't know, ie. tcp syn flag or ports).  If the
  49 -        * rule is also a fragment-specific rule, non-fragments won't
  50 -        * match it. */
  51 -       acpar.fragoff = ntohs(ip->frag_off) & IP_OFFSET;
  52 -       acpar.thoff   = ip_hdrlen(skb);
  53 -       acpar.hotdrop = false;
  54 -       acpar.net     = state->net;
  55 -       acpar.in      = state->in;
  56 -       acpar.out     = state->out;
  57 -       acpar.family  = NFPROTO_IPV4;
  58 -       acpar.hooknum = hook;
  59 -
  60         IP_NF_ASSERT(table->valid_hooks & (1 << hook));
  61         local_bh_disable();
  62 -       addend = xt_write_recseq_begin();
  63         private = table->private;
  64         cpu        = smp_processor_id();
  65         /*
  66 @@ -304,6 +311,23 @@ ipt_do_table(struct sk_buff *skb,
  67          */
  68         smp_read_barrier_depends();
  69         table_base = private->entries;
  70 +
  71 +       e = get_entry(table_base, private->hook_entry[hook]);
  72 +       if (ipt_handle_default_rule(e, &verdict)) {
  73 +               struct xt_counters *counter;
  74 +
  75 +               counter = xt_get_this_cpu_counter(&e->counters);
  76 +               ADD_COUNTER(*counter, skb->len, 1);
  77 +               local_bh_enable();
  78 +               return verdict;
  79 +       }
  80 +
  81 +       stackidx = 0;
  82 +       ip = ip_hdr(skb);
  83 +       indev = state->in ? state->in->name : nulldevname;
  84 +       outdev = state->out ? state->out->name : nulldevname;
  85 +
  86 +       addend = xt_write_recseq_begin();
  87         jumpstack  = (struct ipt_entry **)private->jumpstack[cpu];
  88
  89         /* Switch to alternate jumpstack if we're being invoked via TEE.
  90 @@ -316,7 +340,20 @@ ipt_do_table(struct sk_buff *skb,
  91         if (static_key_false(&xt_tee_enabled))
  92                 jumpstack += private->stacksize * __this_cpu_read(nf_skb_duplicated);
  93
  94 -       e = get_entry(table_base, private->hook_entry[hook]);
  95 +       /* We handle fragments by dealing with the first fragment as
  96 +        * if it was a normal packet.  All other fragments are treated
  97 +        * normally, except that they will NEVER match rules that ask
  98 +        * things we don't know, ie. tcp syn flag or ports).  If the
  99 +        * rule is also a fragment-specific rule, non-fragments won't
 100 +        * match it. */
 101 +       acpar.fragoff = ntohs(ip->frag_off) & IP_OFFSET;
 102 +       acpar.thoff   = ip_hdrlen(skb);
 103 +       acpar.hotdrop = false;
 104 +       acpar.net     = state->net;
 105 +       acpar.in      = state->in;
 106 +       acpar.out     = state->out;
 107 +       acpar.family  = NFPROTO_IPV4;
 108 +       acpar.hooknum = hook;
 109
 110         do {
 111                 const struct xt_entry_target *t;