X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/firewall/blobdiff_plain/20106bbbbe547861538c865ff88a9af0fbe68ad4..ecdca1312d3214c5039e7f783330a90bbfeae2db:/functions.m4

diff --git a/functions.m4 b/functions.m4
index 80caf1d..85afc10 100644
--- a/functions.m4
+++ b/functions.m4
@@ -126,6 +126,20 @@ conntrack () {
   run iptables -A $chain -p tcp ! --syn -g bad-tcp
 }
 
+## commonrules CHAIN
+##
+## Add standard IP filtering rules to the CHAIN.
+commonrules () {
+  set -e
+  chain=$1
+
+  ## Pass fragments through, assuming that the eventual destination will sort
+  ## things out properly.  Except for TCP, that is, which should never be
+  ## fragmented.
+  run iptables -A $chain -p tcp -f -g tcp-fragment
+  run iptables -A $chain -f -j ACCEPT
+}
+
 ## allowservices CHAIN PROTO SERVICE ...
 ##
 ## Add rules to allow the SERVICES on the CHAIN.