Re: [PATCH v4 net-next] net:sched: add action inheritdsfield to skbedit

[Jamal Hadi Salim]

Hi Qiaobin,

Per my previous comments, why do we need the
TCA_SKBEDIT_FLAGS TLV? Isnt SKBEDIT_F_INHERITDSFIELD
sufficient? i.e in tcf_skbedit_init() check for
d->flags&SKBEDIT_F_INHERITDSFIELD then set skb->priority
and flags|=SKBEDIT_F_INHERITDSFIELD

Side note:
Infact the whole flags setting in the init function
seems to be a redundant given all the TLVs have
d->flags also set by user space.
But thats a different patch.

cheers,
jamal

On 12/06/18 11:42 AM, 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>
---

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))