Re: [PATCH net-next v4 1/2] net sched actions: dump more than TCA_ACT_MAX_PRIO actions per batch

[Jamal Hadi Salim]

On 17-04-19 08:36 AM, Jiri Pirko wrote:

Wed, Apr 19, 2017 at 01:57:29PM CEST, j...@mojatatu.com wrote:

From: Jamal Hadi Salim <j...@mojatatu.com>

include/uapi/linux/rtnetlink.h | 21 +++++++++++++++++++--
net/sched/act_api.c            | 43 ++++++++++++++++++++++++++++++++----------
3 files changed, 53 insertions(+), 12 deletions(-)

diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index cce0613..c7080ec 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -674,10 +674,27 @@ struct tcamsg {
        unsigned char   tca__pad1;
        unsigned short  tca__pad2;
};
+
+enum {
+       TCAA_UNSPEC,
+       TCAA_ACT_TAB,
+       TCAA_ACT_FLAGS,
+       TCAA_ACT_COUNT,
+       __TCAA_MAX
+};
+
+#define TCAA_MAX (__TCAA_MAX - 1)
#define TA_RTA(r)  ((struct rtattr*)(((char*)(r)) + NLMSG_ALIGN(sizeof(struct 
tcamsg))))
#define TA_PAYLOAD(n) NLMSG_PAYLOAD(n,sizeof(struct tcamsg))
-#define TCA_ACT_TAB 1 /* attr type must be >=1 */   
-#define TCAA_MAX 1
+#define TCA_ACT_TAB TCAA_ACT_TAB

This is mess. What does "TCAA" stand for?

TC Actions Attributes.  What would you call it? I could have
called it TCA_ROOT etc. But maybe a comment to just call it
TC Actions Attributes would be enough?

I suggest some more meaningful naming of the enum items and define
TCA_ACT_TAB and TCAA_MAX to the new values in order to maintain UAPI

Thats what the above does (for UAPI) maintainance, no?

Also, please put X_MAX = __X_MAX - 1 into enum

That is diverting from the norm which defines it outside
of the enum. A good reason could be: You, Jiri, plan to go and
cleanup all the netlink stuff which uses this style.
Or you think we should start a trend which leads us
to a new clean style.

+/* tcamsg flags stored in attribute TCAA_ACT_FLAGS
+ *
+ * ACT_LARGE_DUMP_ON user->kernel to request for larger than TCA_ACT_MAX_PRIO
+ * actions in a dump. All dump responses will contain the number of actions
+ * being dumped stored in for user app's consumption in TCAA_ACT_COUNT
+ *
+ */
+#define ACT_LARGE_DUMP_ON              (1 << 0)

Use "BIT(0)"

Same question as before.
Are you planning to cleanup the rest of the code which
follows the same style? example, look at this:
        TCA_FLOWER_KEY_FLAGS_IS_FRAGMENT = (1 << 0),

Also use the same prefix as for the enum.

+ you can have each potential flag as a separate u8 attribute. That is the
clearest approach and easily extendable. That's how we do it in devlink
for example.

So you are using 8 bits for one flag which requires one bit?
+ the TLV header? Sounds like overkill.
Note: We dont need more than 1 or 2 bits for this case.
Even 32 bits is overkill for what I am doing.
When do i need to extend a single bit representation?

        struct net *net = sock_net(skb->sk);
-       struct nlattr *tca[TCA_ACT_MAX + 1];
+       struct nlattr *tca[TCAA_MAX + 1];

This is certainly wrong.

Why is it wrong?

        u32 portid = skb ? NETLINK_CB(skb).portid : 0;
        int ret = 0, ovr = 0;

@@ -1005,7 +1014,7 @@ static int tc_ctl_action(struct sk_buff *skb, struct 
nlmsghdr *n,
            !netlink_capable(skb, CAP_NET_ADMIN))
                return -EPERM;

-       ret = nlmsg_parse(n, sizeof(struct tcamsg), tca, TCA_ACT_MAX, NULL,
+       ret = nlmsg_parse(n, sizeof(struct tcamsg), tca, TCAA_MAX, tcaa_policy,

This is certainly wrong.

Same question as above.

+               if (nla_put_u32(skb, TCAA_ACT_COUNT, cb->args[1]))
+                       goto out_module_put;
+               cb->args[1] = 0;

Why you need to zero this?

The count is per submitted message - every time we succesfuly send a msg
to user, we start the recount.

cheers,
jamal