[PATCH] don't use xchg on unaligned stuff

[David S. Miller]

This was caught by the s390 folks and this is the fix I'm
using in my tree.

--- ipt_REJECT.c.~1~    Mon Oct  1 19:22:36 2001
+++ ipt_REJECT.c        Mon Feb 25 14:11:19 2002
@@ -39,7 +39,8 @@
        struct tcphdr *otcph, *tcph;
        struct rtable *rt;
        unsigned int otcplen;
-       u_int16_t tmp;
+       u_int16_t tmp_port;
+       u_int32_t tmp_addr;
        int needs_ack;
 
        /* IP header checks: fragment, too short. */
@@ -78,10 +79,12 @@
        tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
 
        /* Swap source and dest */
-       nskb->nh.iph->daddr = xchg(&nskb->nh.iph->saddr, nskb->nh.iph->daddr);
-       tmp = tcph->source;
+       tmp_addr = nskb->nh.iph->saddr;
+       nskb->nh.iph->saddr = nskb->nh.iph->daddr;
+       nskb->nh.iph->daddr = tmp_addr;
+       tmp_port = tcph->source;
        tcph->source = tcph->dest;
-       tcph->dest = tmp;
+       tcph->dest = tmp_port;
 
        /* Truncate to length (no data) */
        tcph->doff = sizeof(struct tcphdr)/4;