Re: [Xen-devel] [PATCH net-next v2 1/3] net: add skb_checksum_setup

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Paul Durrant [mailto:paul.durrant@xxxxxxxxxx]
> Sent: 09 January 2014 10:03
> To: netdev@xxxxxxxxxxxxxxx; xen-devel@xxxxxxxxxxxxx
> Cc: Paul Durrant; David Miller; Eric Dumazet; Veaceslav Falico; Alexander
> Duyck; Nicolas Dichtel
> Subject: [PATCH net-next v2 1/3] net: add skb_checksum_setup
> 
> This patch adds a function to set up the partial checksum offset for IP
> packets (and optionally re-calculate the pseudo-header checksum) into the
> core network code.
> The implementation was previously private and duplicated between xen-
> netback
> and xen-netfront, however it is not xen-specific and is potentially useful
> to any network driver.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> Cc: David Miller <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Veaceslav Falico <vfalico@xxxxxxxxxx>
> Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
> Cc: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>

Ping?

  Paul

> ---
>  include/linux/skbuff.h |    2 +
>  net/core/skbuff.c      |  273
> ++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 275 insertions(+)
> 
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index d97f2d0..48b7605 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -2893,6 +2893,8 @@ static inline void skb_checksum_none_assert(const
> struct sk_buff *skb)
> 
>  bool skb_partial_csum_set(struct sk_buff *skb, u16 start, u16 off);
> 
> +int skb_checksum_setup(struct sk_buff *skb, bool recalculate);
> +
>  u32 __skb_get_poff(const struct sk_buff *skb);
> 
>  /**
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 1d641e7..15057d2 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -65,6 +65,7 @@
>  #include <net/dst.h>
>  #include <net/sock.h>
>  #include <net/checksum.h>
> +#include <net/ip6_checksum.h>
>  #include <net/xfrm.h>
> 
>  #include <asm/uaccess.h>
> @@ -3549,6 +3550,278 @@ bool skb_partial_csum_set(struct sk_buff *skb,
> u16 start, u16 off)
>  }
>  EXPORT_SYMBOL_GPL(skb_partial_csum_set);
> 
> +static int skb_maybe_pull_tail(struct sk_buff *skb, unsigned int len,
> +                            unsigned int max)
> +{
> +     if (skb_headlen(skb) >= len)
> +             return 0;
> +
> +     /* If we need to pullup then pullup to the max, so we
> +      * won't need to do it again.
> +      */
> +     if (max > skb->len)
> +             max = skb->len;
> +
> +     if (__pskb_pull_tail(skb, max - skb_headlen(skb)) == NULL)
> +             return -ENOMEM;
> +
> +     if (skb_headlen(skb) < len)
> +             return -EPROTO;
> +
> +     return 0;
> +}
> +
> +/* This value should be large enough to cover a tagged ethernet header
> plus
> + * maximally sized IP and TCP or UDP headers.
> + */
> +#define MAX_IP_HDR_LEN 128
> +
> +static int skb_checksum_setup_ip(struct sk_buff *skb, bool recalculate)
> +{
> +     unsigned int off;
> +     bool fragment;
> +     int err;
> +
> +     fragment = false;
> +
> +     err = skb_maybe_pull_tail(skb,
> +                               sizeof(struct iphdr),
> +                               MAX_IP_HDR_LEN);
> +     if (err < 0)
> +             goto out;
> +
> +     if (ip_hdr(skb)->frag_off & htons(IP_OFFSET | IP_MF))
> +             fragment = true;
> +
> +     off = ip_hdrlen(skb);
> +
> +     err = -EPROTO;
> +
> +     if (fragment)
> +             goto out;
> +
> +     switch (ip_hdr(skb)->protocol) {
> +     case IPPROTO_TCP:
> +             err = skb_maybe_pull_tail(skb,
> +                                       off + sizeof(struct tcphdr),
> +                                       MAX_IP_HDR_LEN);
> +             if (err < 0)
> +                     goto out;
> +
> +             if (!skb_partial_csum_set(skb, off,
> +                                       offsetof(struct tcphdr, check))) {
> +                     err = -EPROTO;
> +                     goto out;
> +             }
> +
> +             if (recalculate)
> +                     tcp_hdr(skb)->check =
> +                             ~csum_tcpudp_magic(ip_hdr(skb)->saddr,
> +                                                ip_hdr(skb)->daddr,
> +                                                skb->len - off,
> +                                                IPPROTO_TCP, 0);
> +             break;
> +     case IPPROTO_UDP:
> +             err = skb_maybe_pull_tail(skb,
> +                                       off + sizeof(struct udphdr),
> +                                       MAX_IP_HDR_LEN);
> +             if (err < 0)
> +                     goto out;
> +
> +             if (!skb_partial_csum_set(skb, off,
> +                                       offsetof(struct udphdr, check))) {
> +                     err = -EPROTO;
> +                     goto out;
> +             }
> +
> +             if (recalculate)
> +                     udp_hdr(skb)->check =
> +                             ~csum_tcpudp_magic(ip_hdr(skb)->saddr,
> +                                                ip_hdr(skb)->daddr,
> +                                                skb->len - off,
> +                                                IPPROTO_UDP, 0);
> +             break;
> +     default:
> +             goto out;
> +     }
> +
> +     err = 0;
> +
> +out:
> +     return err;
> +}
> +
> +/* 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 skb_checksum_setup_ipv6(struct sk_buff *skb, bool recalculate)
> +{
> +     int err;
> +     u8 nexthdr;
> +     unsigned int off;
> +     unsigned int len;
> +     bool fragment;
> +     bool done;
> +
> +     fragment = false;
> +     done = false;
> +
> +     off = sizeof(struct ipv6hdr);
> +
> +     err = skb_maybe_pull_tail(skb, off, MAX_IPV6_HDR_LEN);
> +     if (err < 0)
> +             goto out;
> +
> +     nexthdr = ipv6_hdr(skb)->nexthdr;
> +
> +     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;
> +
> +                     err = skb_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;
> +
> +                     err = skb_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;
> +
> +                     err = skb_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 += sizeof(struct frag_hdr);
> +                     break;
> +             }
> +             default:
> +                     done = true;
> +                     break;
> +             }
> +     }
> +
> +     err = -EPROTO;
> +
> +     if (!done || fragment)
> +             goto out;
> +
> +     switch (nexthdr) {
> +     case IPPROTO_TCP:
> +             err = skb_maybe_pull_tail(skb,
> +                                       off + sizeof(struct tcphdr),
> +                                       MAX_IPV6_HDR_LEN);
> +             if (err < 0)
> +                     goto out;
> +
> +             if (!skb_partial_csum_set(skb, off,
> +                                       offsetof(struct tcphdr, check))) {
> +                     err = -EPROTO;
> +                     goto out;
> +             }
> +
> +             if (recalculate)
> +                     tcp_hdr(skb)->check =
> +                             ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> +                                              &ipv6_hdr(skb)->daddr,
> +                                              skb->len - off,
> +                                              IPPROTO_TCP, 0);
> +             break;
> +     case IPPROTO_UDP:
> +             err = skb_maybe_pull_tail(skb,
> +                                       off + sizeof(struct udphdr),
> +                                       MAX_IPV6_HDR_LEN);
> +             if (err < 0)
> +                     goto out;
> +
> +             if (!skb_partial_csum_set(skb, off,
> +                                       offsetof(struct udphdr, check))) {
> +                     err = -EPROTO;
> +                     goto out;
> +             }
> +
> +             if (recalculate)
> +                     udp_hdr(skb)->check =
> +                             ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
> +                                              &ipv6_hdr(skb)->daddr,
> +                                              skb->len - off,
> +                                              IPPROTO_UDP, 0);
> +             break;
> +     default:
> +             goto out;
> +     }
> +
> +     err = 0;
> +
> +out:
> +     return err;
> +}
> +
> +/**
> + * skb_checksum_setup - set up partial checksum offset
> + * @skb: the skb to set up
> + * @recalculate: if true the pseudo-header checksum will be recalculated
> + */
> +int skb_checksum_setup(struct sk_buff *skb, bool recalculate)
> +{
> +     int err;
> +
> +     switch (skb->protocol) {
> +     case htons(ETH_P_IP):
> +             err = skb_checksum_setup_ip(skb, recalculate);
> +             break;
> +
> +     case htons(ETH_P_IPV6):
> +             err = skb_checksum_setup_ipv6(skb, recalculate);
> +             break;
> +
> +     default:
> +             err = -EPROTO;
> +             break;
> +     }
> +
> +     return err;
> +}
> +EXPORT_SYMBOL(skb_checksum_setup);
> +
>  void __skb_warn_lro_forwarding(const struct sk_buff *skb)
>  {
>       net_warn_ratelimited("%s: received packets cannot be forwarded
> while LRO is enabled\n",
> --
> 1.7.10.4


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