[NETFILTER]: x_tables: add rateest match

Add rate estimator match. The rate estimator match can match on
estimated rates by the RATEEST target. It supports matching on
absolute bps/pps values, comparing two rate estimators and matching
on the difference between two rate estimators.

This is what I use to route outgoing data connections from a FTP
server over two lines based on the  available bandwidth:

# estimate outgoing rates
iptables -t mangle -A POSTROUTING -o eth0 -j RATEEST --rateest-name eth0 \
                                                     --rateest-interval 250ms \
                                                     --rateest-ewma 0.5s
iptables -t mangle -A POSTROUTING -o ppp0 -j RATEEST --rateest-name ppp0 \
                                                     --rateest-interval 250ms \
                                                     --rateest-ewma 0.5s

# mark based on available bandwidth
iptables -t mangle -A BALANCE -m state --state NEW \
                              -m helper --helper ftp \
                              -m rateest --rateest-delta \
                                         --rateest1 eth0 \
                                         --rateest-bps1 2.5mbit \
                                         --rateest-gt \
                                         --rateest2 ppp0 \
                                         --rateest-bps2 2mbit \
                              -j CONNMARK --set-mark 0x1

iptables -t mangle -A BALANCE -m state --state NEW \
                              -m helper --helper ftp \
                              -m rateest --rateest-delta \
                                         --rateest1 ppp0 \
                                         --rateest-bps1 2mbit \
                                         --rateest-gt \
                                         --rateest2 eth0 \
                                         --rateest-bps2 2.5mbit \
                              -j CONNMARK --set-mark 0x2

iptables -t mangle -A BALANCE -j CONNMARK --restore-mark

Signed-off-by: Patrick McHardy <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 413afaa..3b9ea8f 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -73,6 +73,7 @@
 obj-$(CONFIG_NETFILTER_XT_MATCH_PKTTYPE) += xt_pkttype.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_POLICY) += xt_policy.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_QUOTA) += xt_quota.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_RATEEST) += xt_rateest.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_REALM) += xt_realm.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_SCTP) += xt_sctp.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_STATE) += xt_state.o