Pull data into headers properly, and checksum ICMP replies correctly.

diff --git a/datapath/nx_act_snat.c b/datapath/nx_act_snat.c
index e577c9d..2d0306a 100644 (file)
--- a/datapath/nx_act_snat.c
+++ b/datapath/nx_act_snat.c
@@ -235,29 +235,28 @@ handle_icmp_snat(struct sk_buff *skb)
 {
        struct net_bridge_port *p = skb->dev->br_port;
        struct ethhdr *eh;
-       struct iphdr *iph = ip_hdr(skb);
+       struct iphdr *iph;
        struct icmphdr *icmph;
-       unsigned int datalen;
        uint8_t tmp_eth[ETH_ALEN];
        uint32_t tmp_ip;
        struct sk_buff *nskb;
 
        /* We're only interested in addresses we rewrite. */
+       iph = ip_hdr(skb);
        if (!snat_this_address(p, iph->daddr)) {
                return 0;
        }
 
-       icmph = (struct icmphdr *) ((u_int32_t *)iph + iph->ihl);
-       datalen = skb->len - iph->ihl * 4;
-
        /* Drop fragments and packets not long enough to hold the ICMP
         * header. */
-       if (((ntohs(iph->frag_off) & IP_OFFSET) != 0) || datalen < 4) 
+       if ((ntohs(iph->frag_off) & IP_OFFSET) != 0 ||
+           !pskb_may_pull(skb, skb_transport_offset(skb) + 4))
                return 0;
 
        /* We only respond to echo requests to our address.  Continue 
         * processing replies and other ICMP messages since they may be 
         * intended for NAT'd hosts. */
+       icmph = icmp_hdr(skb);
        if (icmph->type != ICMP_ECHO)
                return 0;
 
@@ -269,19 +268,31 @@ handle_icmp_snat(struct sk_buff *skb)
                return -1;
        }
 
+       /* Update Ethernet header. */
        eh = eth_hdr(nskb);
-       iph = ip_hdr(nskb);
-       icmph = (struct icmphdr *) ((u_int32_t *)iph + iph->ihl);
+       memcpy(tmp_eth, eh->h_dest, ETH_ALEN);
+       memcpy(eh->h_dest, eh->h_source, ETH_ALEN);
+       memcpy(eh->h_source, tmp_eth, ETH_ALEN);
 
+       /* Update IP header.
+        * This is kind of busted, at least in that it doesn't check that the
+        * echoed IP options make sense. */
+       iph = ip_hdr(nskb);
+       iph->id = 0;
+       iph->frag_off = 0;
+       iph->ttl = IPDEFTTL;
+       iph->check = 0;
        tmp_ip = iph->daddr;
        iph->daddr = iph->saddr;
        iph->saddr = tmp_ip;
+       iph->check = ip_fast_csum(iph, iph->ihl);
 
-       memcpy(tmp_eth, eh->h_dest, ETH_ALEN);
-       memcpy(eh->h_dest, eh->h_source, ETH_ALEN);
-       memcpy(eh->h_source, tmp_eth, ETH_ALEN);
-       
+       /* Update ICMP header. */
+       icmph = icmp_hdr(nskb);
        icmph->type = ICMP_ECHOREPLY;
+       icmph->checksum = 0;
+       icmph->checksum = ip_compute_csum(icmph,
+                                         nskb->tail - nskb->transport_header);
 
        dp_xmit_skb_push(nskb);
 
@@ -303,6 +314,7 @@ snat_pre_route(struct sk_buff *skb)
        struct iphdr *iph;
        int len;
 
+       WARN_ON_ONCE(skb_network_offset(skb));
        if (skb->protocol == htons(ETH_P_ARP)) 
                return handle_arp_snat(skb);
        else if (skb->protocol != htons(ETH_P_IP)) 
@@ -315,14 +327,17 @@ snat_pre_route(struct sk_buff *skb)
        if (iph->ihl < 5 || iph->version != 4)
                goto ipv4_error;
 
-       if (!pskb_may_pull(skb, iph->ihl*4))
+       if (!pskb_may_pull(skb, ip_hdrlen(skb)))
                goto ipv4_error;
+       skb_set_transport_header(skb, ip_hdrlen(skb));
 
        /* Check if we need to echo reply for this address */
+       iph = ip_hdr(skb);
        if ((iph->protocol == IPPROTO_ICMP) && (handle_icmp_snat(skb))) 
                return -1;
 
-       if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
+       iph = ip_hdr(skb);
+       if (unlikely(ip_fast_csum(iph, iph->ihl)))
                goto ipv4_error;
 
        len = ntohs(iph->tot_len);