I cannot shape the ip xxx.xxx.xxx.xxx when I do SNAT or MASQUERADE with them. Otherwise when I remove these two iptables lines the shaping works perfectly.

It is very important for me to shape the xxx.xxx.xxx.xxx ip and not the yyy.yyy.yyy.yyy. When I tried to shape yyy.yyy.yyy.yyy, it worked.

What rules should be added to make this possible?
My iptables rules are:

iptables -A PREROUTING -t mangle -s xxx.xxx.xxx.xxx -j MARK  --set-mark 1
iptables -A POSTROUTING -t nat -s xxx.xxx.xxx.xxx -j SNAT --to zzz.zzz.zzz.zzz -o eth4

iptables -t mangle -I PREROUTING -j IMQ
ip link set imq0 up

ip rule shows the following output:

32764:  from zzz.zzz.zzz.0/24 lookup ew
32765:  from all fwmark        1 lookup ew
32766:  from all lookup main
32767:  from all lookup default

My tc + htb rule look like this:

/sbin/tc qdisc add dev imq0 root handle 1: htb default 200 r2q 3
/sbin/tc class add dev imq0 parent 1:0 classid 1:1 htb rate 100Mbit ceil 100Mbit burst 2k prio 5
/sbin/tc filter add dev imq0 parent 1:0 protocol ip prio 5 handle 1: u32 divisor 256
/sbin/tc class add dev imq0 parent 1:1 classid 1:2 htb rate 512kbit ceil 512kbit burst 2k prio 5
/sbin/tc qdisc add dev imq0 parent 1:2 handle 10: sfq quantum 1514b perturb 10
/sbin/tc filter add dev imq0 parent 1:0 protocol ip prio 5 u32 match ip dst xxx.xxx.xxx.xxx flowid 1:2

If i understood you right this is probably not working because imq sees packets before zzz.zzz.zzz.zzz is dnated back to xxx.xxx.xxx.xxx. please try the attached patch.

--- imq.c.orig  Sun Aug 11 15:30:24 2002
+++ imq.c       Sun Aug 11 15:31:17 2002
@@ -37,7 +37,7 @@
        imq_nf_hook,
        PF_INET,
        NF_IP_PRE_ROUTING,
-       NF_IP_PRI_MANGLE + 1
+       NF_IP_PRI_NAT_DST + 1
 };
 
 static struct nf_hook_ops imq_egress_ipv4 = {
@@ -54,7 +54,7 @@
        imq_nf_hook,
        PF_INET6,
        NF_IP6_PRE_ROUTING,
-       NF_IP6_PRI_MANGLE + 1
+       NF_IP6_PRI_NAT_DST + 1
 };
 
 static struct nf_hook_ops imq_egress_ipv6 = {