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

[annie li <annie.li@xxxxxxxxxx>]

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

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