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Date: Fri, 28 Dec 2007 17:08:38 +0100
From: Patrick McHardy <kaber@...sh.net>
To: Ariane Keller <ariane.keller@....ee.ethz.ch>
CC: Ben Greear <greearb@...delatech.com>,
Stephen Hemminger <shemminger@...ux-foundation.org>,
netdev@...r.kernel.org, Rainer Baumann <baumann@....ee.ethz.ch>
Subject: Re: [PATCH 0/2] netem: trace enhancement: kernel
Ariane Keller wrote:
> +struct tc_netem_stats
> +{
> + int packetcount;
> + int packetok;
> + int normaldelay;
> + int drops;
> + int dupl;
> + int corrupt;
> + int novaliddata;
> + int reloadbuffer;
These should be unsigned int or __u32.
>
> diff -uprN -X linux-2.6.23.8/Documentation/dontdiff
> linux-2.6.23.8/include/net/flowseed.h
> linux-2.6.23.8_mod/include/net/flowseed.h
> --- linux-2.6.23.8/include/net/flowseed.h 1970-01-01
> 01:00:00.000000000 +0100
> +++ linux-2.6.23.8_mod/include/net/flowseed.h 2007-12-21
> 19:43:24.000000000 +0100
> @@ -0,0 +1,34 @@
> +/* flowseed.h header file for the netem trace enhancement
> + */
> +
> +#ifndef _FLOWSEED_H
> +#define _FLOWSEED_H
> +#include <net/sch_generic.h>
> +
> +/* must be divisible by 4 (=#pkts)*/
> +#define DATA_PACKAGE 4000
Its not obvious that this refers to a size, please rename
to something more approriate. And why is it hardcoded
to 4000? Shouldn't it be related to NLMSG_GOODSIZE?
> +#define DATA_PACKAGE_ID 4008
Its even less obvious that this is the netlink attribute
size. Its obfuscation anyway, just open-code
RTA_SPACE(new name of DATA_PACKAGE).
> +
> +/* struct per flow - kernel */
> +struct tcn_control
> +{
> + struct list_head full_buffer_list;
> + struct list_head empty_buffer_list;
> + struct buflist * buffer_in_use;
> + int *offsetpos; /* pointer to actual pos in the buffer in
> use */
> + int flowid;
> +};
> +
> +struct tcn_statistic
> +{
> + int packetcount;
> + int packetok;
> + int normaldelay;
> + int drops;
> + int dupl;
> + int corrupt;
> + int novaliddata;
> + int reloadbuffer;
Also unsigned please.
>
> diff -uprN -X linux-2.6.23.8/Documentation/dontdiff
> linux-2.6.23.8/net/sched/sch_api.c linux-2.6.23.8_mod/net/sched/sch_api.c
> --- linux-2.6.23.8/net/sched/sch_api.c 2007-11-16
> 19:14:27.000000000 +0100
> +++ linux-2.6.23.8_mod/net/sched/sch_api.c 2007-12-21
> 19:42:49.000000000 +0100
> @@ -28,6 +28,7 @@
> #include <linux/list.h>
> #include <linux/hrtimer.h>
>
> +#include <net/sock.h>
> #include <net/netlink.h>
> #include <net/pkt_sched.h>
>
> @@ -841,6 +842,62 @@ rtattr_failure:
> nlmsg_trim(skb, b);
> return -1;
> }
> +static int tc_fill(struct sk_buff *skb, struct Qdisc *q, u32 clid,
> + u32 pid, u32 seq, u16 flags, int event)
> +{
> + struct tcmsg *tcm;
> + struct nlmsghdr *nlh;
> + unsigned char *b = skb_tail_pointer(skb);
> +
> + nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*tcm), flags);
> + tcm = NLMSG_DATA(nlh);
> + tcm->tcm_family = AF_UNSPEC;
> + tcm->tcm__pad1 = 0;
> + tcm->tcm__pad2 = 0;
> + tcm->tcm_ifindex = q->dev->ifindex;
> + tcm->tcm_parent = clid;
> + tcm->tcm_handle = q->handle;
> + tcm->tcm_info = atomic_read(&q->refcnt);
> + RTA_PUT(skb, TCA_KIND, IFNAMSIZ, q->ops->id);
> + if (q->ops->dump && q->ops->dump(q, skb) < 0)
> + goto rtattr_failure;
> +
> + nlh->nlmsg_len = skb_tail_pointer(skb) - b;
> +
> + return skb->len;
Why is this function not used by tc_fill_qdisc?
> +
> +nlmsg_failure:
> +rtattr_failure:
> + nlmsg_trim(skb, b);
> + return -1;
> +}
> +
> +int qdisc_notify_pid(int pid, struct nlmsghdr *n,
> + u32 clid, struct Qdisc *old, struct Qdisc *new)
> +{
> + struct sk_buff *skb;
> + skb = alloc_skb(NLMSG_GOODSIZE, gfp_any());
> + if (!skb)
> + return -ENOBUFS;
> +
> + if (old && old->handle) {
> + if (tc_fill(skb, old, clid, pid, n->nlmsg_seq,
> + 0, RTM_DELQDISC) < 0)
> + goto err_out;
> + }
> + if (new) {
> + if (tc_fill(skb, new, clid, pid, n->nlmsg_seq,
> + old ? NLM_F_REPLACE : 0, RTM_NEWQDISC) < 0)
> + goto err_out;
> + }
> + if (skb->len)
> + return rtnetlink_send(skb, pid, RTNLGRP_TC, n->nlmsg_flags);
And why do you need a new notification function? qdisc_notify
seems perfectly fine for this.
> +
> +err_out:
> + kfree_skb(skb);
> + return -EINVAL;
> +}
> +EXPORT_SYMBOL(qdisc_notify_pid);
>
> static int qdisc_notify(struct sk_buff *oskb, struct nlmsghdr *n,
> u32 clid, struct Qdisc *old, struct Qdisc *new)
> @@ -848,7 +905,7 @@ static int qdisc_notify(struct sk_buff *
> struct sk_buff *skb;
> u32 pid = oskb ? NETLINK_CB(oskb).pid : 0;
>
> - skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
> + skb = alloc_skb(NLMSG_GOODSIZE, gfp_any());
You don't even use qdisc_notify anywhere in your patch, why
this change?
> if (!skb)
> return -ENOBUFS;
>
> diff -uprN -X linux-2.6.23.8/Documentation/dontdiff
> linux-2.6.23.8/net/sched/sch_netem.c
> linux-2.6.23.8_mod/net/sched/sch_netem.c
> --- linux-2.6.23.8/net/sched/sch_netem.c 2007-11-16
> 19:14:27.000000000 +0100
> +++ linux-2.6.23.8_mod/net/sched/sch_netem.c 2007-12-21
> 19:42:49.000000000 +0100
> +/* don't call this function directly. It is called after
> + * a packet has been taken out of a buffer and it was the last.
> + */
> +static int reload_flowbuffer(struct netem_sched_data *q, struct Qdisc
> *sch)
> +{
> + struct tcn_control *flow = q->flowbuffer;
> + struct nlmsghdr n;
> + struct buflist *element = list_entry(flow->full_buffer_list.next,
> + struct buflist, list);
> + /* the current buffer is empty */
> + list_add_tail(&flow->buffer_in_use->list, &flow->empty_buffer_list);
> +
> + if (list_empty(&q->flowbuffer->full_buffer_list)) {
> + printk(KERN_ERR "netem: reload_flowbuffer, no full buffer\n");
> + return -EFAULT;
> + }
> +
> + list_del_init(&element->list);
> + flow->buffer_in_use = element;
> + flow->offsetpos = (int *)element->buf;
> + memset(&n, 0, sizeof(struct nlmsghdr));
> + n.nlmsg_seq = 1;
> + n.nlmsg_flags = NLM_F_REQUEST;
This netlink header faking is horrible, please just change qdisc_notify
to deal with absent netlink headers appropriately. The sequence number
used for kernel notifications not related to userspace requests is 0.
> + if (qdisc_notify_pid(q->flowid, &n, sch->parent, NULL, sch) < 0)
> + printk(KERN_ERR "netem: unable to request for more data\n");
netlink_set_err() causing userspace to request all current information
seems like better error handling. The remaining netem part also looks
like it could use a lot of improvement, you shouldn't need manual
notifications on destruction, change, etc., all this is already
handled by sch_api. There should be a single new notification in
netem_enqueue(), calling qdisc_notify(), which dumps the current
state to userspace.
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