Re: [PATCH net v5] xen-netback: fix fragment detection in checksum setup

On 2013/12/4 1:39, Paul Durrant wrote:

  
+/* This value should be large enough to cover a tagged ethernet header plus
+ * an IPv6 header, all options, and a maximal TCP or UDP header.
+ */
+#define MAX_IPV6_HDR_LEN 256
+
+#define OPT_HDR(type, skb, off) \
+	(type *)(skb_network_header(skb) + (off))
+
  static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb,
  			       int recalculate_partial_csum)
  {
-	int err = -EPROTO;
-	struct ipv6hdr *ipv6h = (void *)skb->data;
+	int err;
  	u8 nexthdr;
-	unsigned int header_size;
  	unsigned int off;
+	unsigned int len;
  	bool fragment;
  	bool done;
  
+	fragment = false;
  	done = false;
  
  	off = sizeof(struct ipv6hdr);
  
-	header_size = skb->network_header + off;
-	maybe_pull_tail(skb, header_size);
+	err = maybe_pull_tail(skb, off, MAX_IPV6_HDR_LEN);
+	if (err < 0)
+		goto out;
  
-	nexthdr = ipv6h->nexthdr;
+	nexthdr = ipv6_hdr(skb)->nexthdr;
  
-	while ((off <= sizeof(struct ipv6hdr) + ntohs(ipv6h->payload_len)) &&
-	       !done) {
+	len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len);
+	while (off <= len && !done) {
  		switch (nexthdr) {
  		case IPPROTO_DSTOPTS:
  		case IPPROTO_HOPOPTS:
  		case IPPROTO_ROUTING: {
-			struct ipv6_opt_hdr *hp = (void *)(skb->data + off);
+			struct ipv6_opt_hdr *hp;
  
-			header_size = skb->network_header +
-				off +
-				sizeof(struct ipv6_opt_hdr);
-			maybe_pull_tail(skb, header_size);
+			err = maybe_pull_tail(skb,
+					      off +
+					      sizeof(struct ipv6_opt_hdr),
+					      MAX_IPV6_HDR_LEN);
+			if (err < 0)
+				goto out;
  
+			hp = OPT_HDR(struct ipv6_opt_hdr, skb, off);
  			nexthdr = hp->nexthdr;
  			off += ipv6_optlen(hp);
  			break;
  		}
  		case IPPROTO_AH: {
-			struct ip_auth_hdr *hp = (void *)(skb->data + off);
+			struct ip_auth_hdr *hp;
+
+			err = maybe_pull_tail(skb,
+					      off +
+					      sizeof(struct ip_auth_hdr),
+					      MAX_IPV6_HDR_LEN);
+			if (err < 0)
+				goto out;
+
+			hp = OPT_HDR(struct ip_auth_hdr, skb, off);
+			nexthdr = hp->nexthdr;
+			off += ipv6_authlen(hp);
+			break;
+		}
+		case IPPROTO_FRAGMENT: {
+			struct frag_hdr *hp;
  
-			header_size = skb->network_header +
-				off +
-				sizeof(struct ip_auth_hdr);
-			maybe_pull_tail(skb, header_size);
+			err = maybe_pull_tail(skb,
+					      off +
+					      sizeof(struct frag_hdr),
+					      MAX_IPV6_HDR_LEN);
+			if (err < 0)
+				goto out;
+
+			hp = OPT_HDR(struct frag_hdr, skb, off);
+
+			if (hp->frag_off & htons(IP6_OFFSET | IP6_MF))
+				fragment = true;
  
  			nexthdr = hp->nexthdr;
-			off += (hp->hdrlen+2)<<2;
+			off += sizeof(struct frag_hdr);
  			break;
  		}
-		case IPPROTO_FRAGMENT:
-			fragment = true;
-			/* fall through */

About IPv6 extension headers, should "Encapsulating Security Payload" be 
processed too?(See rfc2460 and rfc2406) Is there any concern to ignore 
it here?

Thanks
Annie