On Tue, Jun 12, 2018 at 03:42:55PM +0000, Fu, Qiaobin wrote:
> The new action inheritdsfield copies the field DS of
> IPv4 and IPv6 packets into skb->priority. This enables
> later classification of packets based on the DS field.
> 
> v4:
> *Not allow setting flags other than the expected ones.
> 
> *Allow dumping the pure flags.
> 
> Original idea by Jamal Hadi Salim <j...@mojatatu.com>
> 
> Signed-off-by: Qiaobin Fu <qiaob...@bu.edu>
> Reviewed-by: Michel Machado <mic...@digirati.com.br>

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com>

> ---
> 
> Note that the motivation for this patch is found in the following discussion:
> https://www.spinics.net/lists/netdev/msg501061.html
> ---
> diff --git a/include/uapi/linux/tc_act/tc_skbedit.h 
> b/include/uapi/linux/tc_act/tc_skbedit.h
> index fbcfe27a4e6c..6de6071ebed6 100644
> --- a/include/uapi/linux/tc_act/tc_skbedit.h
> +++ b/include/uapi/linux/tc_act/tc_skbedit.h
> @@ -30,6 +30,7 @@
>  #define SKBEDIT_F_MARK                       0x4
>  #define SKBEDIT_F_PTYPE                      0x8
>  #define SKBEDIT_F_MASK                       0x10
> +#define SKBEDIT_F_INHERITDSFIELD     0x20
>  
>  struct tc_skbedit {
>       tc_gen;
> @@ -45,6 +46,7 @@ enum {
>       TCA_SKBEDIT_PAD,
>       TCA_SKBEDIT_PTYPE,
>       TCA_SKBEDIT_MASK,
> +     TCA_SKBEDIT_FLAGS,
>       __TCA_SKBEDIT_MAX
>  };
>  #define TCA_SKBEDIT_MAX (__TCA_SKBEDIT_MAX - 1)
> diff --git a/net/sched/act_skbedit.c b/net/sched/act_skbedit.c
> index 6138d1d71900..9adbcfa3f5fe 100644
> --- a/net/sched/act_skbedit.c
> +++ b/net/sched/act_skbedit.c
> @@ -23,6 +23,9 @@
>  #include <linux/rtnetlink.h>
>  #include <net/netlink.h>
>  #include <net/pkt_sched.h>
> +#include <net/ip.h>
> +#include <net/ipv6.h>
> +#include <net/dsfield.h>
>  
>  #include <linux/tc_act/tc_skbedit.h>
>  #include <net/tc_act/tc_skbedit.h>
> @@ -41,6 +44,25 @@ static int tcf_skbedit(struct sk_buff *skb, const struct 
> tc_action *a,
>  
>       if (d->flags & SKBEDIT_F_PRIORITY)
>               skb->priority = d->priority;
> +     if (d->flags & SKBEDIT_F_INHERITDSFIELD) {
> +             int wlen = skb_network_offset(skb);
> +
> +             switch (tc_skb_protocol(skb)) {
> +             case htons(ETH_P_IP):
> +                     wlen += sizeof(struct iphdr);
> +                     if (!pskb_may_pull(skb, wlen))
> +                             goto err;
> +                     skb->priority = ipv4_get_dsfield(ip_hdr(skb)) >> 2;
> +                     break;
> +
> +             case htons(ETH_P_IPV6):
> +                     wlen += sizeof(struct ipv6hdr);
> +                     if (!pskb_may_pull(skb, wlen))
> +                             goto err;
> +                     skb->priority = ipv6_get_dsfield(ipv6_hdr(skb)) >> 2;
> +                     break;
> +             }
> +     }
>       if (d->flags & SKBEDIT_F_QUEUE_MAPPING &&
>           skb->dev->real_num_tx_queues > d->queue_mapping)
>               skb_set_queue_mapping(skb, d->queue_mapping);
> @@ -53,6 +75,10 @@ static int tcf_skbedit(struct sk_buff *skb, const struct 
> tc_action *a,
>  
>       spin_unlock(&d->tcf_lock);
>       return d->tcf_action;
> +
> +err:
> +     spin_unlock(&d->tcf_lock);
> +     return TC_ACT_SHOT;
>  }
>  
>  static const struct nla_policy skbedit_policy[TCA_SKBEDIT_MAX + 1] = {
> @@ -62,6 +88,7 @@ static const struct nla_policy 
> skbedit_policy[TCA_SKBEDIT_MAX + 1] = {
>       [TCA_SKBEDIT_MARK]              = { .len = sizeof(u32) },
>       [TCA_SKBEDIT_PTYPE]             = { .len = sizeof(u16) },
>       [TCA_SKBEDIT_MASK]              = { .len = sizeof(u32) },
> +     [TCA_SKBEDIT_FLAGS]             = { .len = sizeof(u64) },
>  };
>  
>  static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
> @@ -73,6 +100,7 @@ static int tcf_skbedit_init(struct net *net, struct nlattr 
> *nla,
>       struct tc_skbedit *parm;
>       struct tcf_skbedit *d;
>       u32 flags = 0, *priority = NULL, *mark = NULL, *mask = NULL;
> +     u64 *pure_flags = NULL;
>       u16 *queue_mapping = NULL, *ptype = NULL;
>       bool exists = false;
>       int ret = 0, err;
> @@ -114,6 +142,12 @@ static int tcf_skbedit_init(struct net *net, struct 
> nlattr *nla,
>               mask = nla_data(tb[TCA_SKBEDIT_MASK]);
>       }
>  
> +     if (tb[TCA_SKBEDIT_FLAGS] != NULL) {
> +             pure_flags = nla_data(tb[TCA_SKBEDIT_FLAGS]);
> +             if (*pure_flags & SKBEDIT_F_INHERITDSFIELD)
> +                     flags |= SKBEDIT_F_INHERITDSFIELD;
> +     }
> +
>       parm = nla_data(tb[TCA_SKBEDIT_PARMS]);
>  
>       exists = tcf_idr_check(tn, parm->index, a, bind);
> @@ -178,6 +212,7 @@ static int tcf_skbedit_dump(struct sk_buff *skb, struct 
> tc_action *a,
>               .action  = d->tcf_action,
>       };
>       struct tcf_t t;
> +     u64 pure_flags = 0;
>  
>       if (nla_put(skb, TCA_SKBEDIT_PARMS, sizeof(opt), &opt))
>               goto nla_put_failure;
> @@ -196,6 +231,11 @@ static int tcf_skbedit_dump(struct sk_buff *skb, struct 
> tc_action *a,
>       if ((d->flags & SKBEDIT_F_MASK) &&
>           nla_put_u32(skb, TCA_SKBEDIT_MASK, d->mask))
>               goto nla_put_failure;
> +     if (d->flags & SKBEDIT_F_INHERITDSFIELD)
> +             pure_flags |= SKBEDIT_F_INHERITDSFIELD;
> +     if (pure_flags != 0 &&
> +         nla_put(skb, TCA_SKBEDIT_FLAGS, sizeof(pure_flags), &pure_flags))
> +             goto nla_put_failure;
>  
>       tcf_tm_dump(&t, &d->tcf_tm);
>       if (nla_put_64bit(skb, TCA_SKBEDIT_TM, sizeof(t), &t, TCA_SKBEDIT_PAD))

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