X-Git-Url: https://git.distorted.org.uk/~mdw/firewall/blobdiff_plain/4eb9f4dfa52db009403bf7a0c018cb5d75ed0052..32110b35da9d3ed1ce9668d3f17c28100a878687:/functions.m4

diff --git a/functions.m4 b/functions.m4
index c3609a5..1cd0db5 100644
--- a/functions.m4
+++ b/functions.m4
@@ -94,12 +94,12 @@ ip46tables () {
 ## Ensure that the named chains exist and are empty.
 clearchain () {
   set -e
-  for chain; do
-    case $chain in
-      *:*) table=${chain%:*} chain=${chain#*:} ;;
+  for _chain; do
+    case $_chain in
+      *:*) table=${_chain%:*} _chain=${_chain#*:} ;;
       *) table=filter ;;
     esac
-    run ip46tables -t $table -N $chain 2>/dev/null || :
+    run ip46tables -t $table -N $_chain 2>/dev/null || :
   done
 }
 
@@ -109,11 +109,19 @@ clearchain () {
 makeset () {
   set -e
   name=$1; shift
-  if ipset -nL | grep -q "^Name: $name$"; then
-    :
-  else
-    ipset -N "$name" "$@"
-  fi
+  v=$(ipset --version)
+  createp=t
+  case "$v" in
+    "ipset v4"*)
+      if ipset -nL | grep -q "^Name: $name\$"; then createp=nil; fi
+      ;;
+    *)
+      if ipset -n -L | grep -q "^$name\$"; then createp=nil; fi
+      ;;
+  esac
+  case $createp in
+    t) ipset -N "$name" "$@" ;;
+  esac
 }
 
 ## errorchain CHAIN ACTION ARGS ...
@@ -130,7 +138,7 @@ errorchain () {
   clearchain $table:$chain
   run ip46tables -t $table -A $chain -j LOG \
 	  -m limit --limit 3/minute --limit-burst 10 \
-	  --log-prefix "fw: $chain " --log-level notice
+	  --log-prefix "fw: $chain " --log-level notice || :
   run ip46tables -t $table -A $chain -j "$@" \
 	  -m limit --limit 20/second --limit-burst 100
   run ip46tables -t $table -A $chain -j DROP
@@ -310,6 +318,26 @@ dnsresolver () {
   done
 }
 
+## dnsserver CHAIN
+##
+## Add rules to allow CHAIN to be a DNS server.
+dnsserver () {
+  set -e
+  chain=$1
+
+  ## Allow TCP access.  Hitting us with SYNs will make us deploy SYN cookies,
+  ## but that's tolerable.
+  run ip46tables -A $chain -j ACCEPT -p tcp --destination-port 53
+
+  ## Avoid being a DDoS amplifier by rate-limiting incoming DNS queries.
+  clearchain $chain-udp-dns
+  run ip46tables -A $chain-udp-dns -j ACCEPT \
+	  -m limit --limit 20/second --limit-burst 300
+  run ip46tables -A $chain-udp-dns -g dns-rate-limit
+  run ip46tables -A $chain -j $chain-udp-dns \
+	  -p udp --destination-port 53
+}
+
 ## openports CHAIN [MIN MAX]
 ##
 ## Add rules to CHAIN to allow the open ports.
@@ -335,7 +363,7 @@ m4_divert(20)m4_dnl
 ###			`defnetclass'.
 ### net_inet_NET	List of IPv4 address ranges in the network.
 ### net_inet6_NET	List of IPv6 address ranges in the network.
-### net_fwd_NET		List of other networks that this one forwards to.
+### net_via_NET		List of other networks that this one forwards via.
 ### net_hosts_NET	List of hosts known to be in the network.
 ### host_inet_HOST	IPv4 address of the named HOST.
 ### host_inet6_HOST	IPv6 address of the named HOST.
@@ -407,9 +435,9 @@ defnetclass () {
 	from=$(( $from + $bit ))
       done
       to=$(( ($netclassindex << $BIT_TO) ))
-      tomask=$(( $MASK_MASK ^ (1 << ($netclassindex + $BIT_MASK)) ))
+      tomask=$(( $MASK_TO | $MASK_MASK ^ (1 << ($netclassindex + $BIT_MASK)) ))
       trace "from $name --> set $(printf %08x/%08x $from $frommask)"
-      trace "  to $name --> and $(printf %08x/%08x $to $tomask)"
+      trace "  to $name --> set $(printf %08x/%08x $to $tomask)"
 
       ## Now establish the mark-from-NAME and mark-to-NAME chains.
       clearchain mangle:mark-from-$name mangle:mark-to-$name
@@ -424,7 +452,7 @@ defnetclass () {
 
 ## defnet NET CLASS
 ##
-## Define a network.  Follow by calls to `addr', `forwards', etc. to define
+## Define a network.  Follow by calls to `addr', `via', etc. to define
 ## properties of the network.  Networks are processed in order, so if their
 ## addresses overlap then the more specific addresses should be defined
 ## earlier.
@@ -447,11 +475,11 @@ addr () {
   done
 }
 
-## forwards NET ...
+## via NET ...
 ##
 ## Declare that packets from this network are forwarded to the other NETs.
-forwards () {
-  eval "net_fwd_$net=\"$*\""
+via () {
+  eval "net_via_$net=\"$*\""
 }
 
 ## noxit NET ...
@@ -539,15 +567,18 @@ iface () {
   done
 }
 
+## matchnets OPT WIN FLAGS PREPARE BASE SUFFIX NEXT NET [NET ...]
+##
 ## Build rules which match a particular collection of networks.
+##
 ## Specifically, use the address-comparison operator OPT (typically `-s' or
-## `-d') to match the addresses of NOT, writing the rules to the chain
-## BASESUFFIX.  If we find a match, dispatch to WIN-CLASS, where CLASS is
-## the class of the matching network.  In order to deal with networks
-## containing negative address ranges, more chains may need to be
-## constructed; they will be named BASE#Q for sequence numbers Q starting
-## with NEXT.  All of this happens on the `mangle' table, and there isn't
-## (currently) a way to tweak this.
+## `-d') to match the addresses of each NET, writing the rules to the chain
+## BASESUFFIX.  If we find a match, dispatch to WIN-CLASS, where CLASS is the
+## class of the matching network.  In order to deal with networks containing
+## negative address ranges, more chains may need to be constructed; they will
+## be named BASE#Q for sequence numbers Q starting with NEXT.  All of this
+## happens on the `mangle' table, and there isn't (currently) a way to tweak
+## this.
 ##
 ## The FLAGS gather additional interesting information about the job,
 ## separated by colons.  The only flag currently is :default: which means
@@ -698,8 +729,8 @@ net_interfaces () {
     nextnets=""
     any=nil
     for net in $nets; do
-      eval fwd=\$net_fwd_$net
-      for n in $fwd; do
+      eval via=\$net_via_$net
+      for n in $via; do
 	case $seen in *":$n:"*) continue ;; esac
 	seen=$seen$n:
 	eval noxit=\$net_noxit_$n