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authorJesper Dangaard Brouer <brouer@redhat.com>2013-08-14 23:47:11 +0200
committerDavid S. Miller <davem@davemloft.net>2013-08-15 01:43:08 -0700
commit8a8e3d84b1719a56f9151909e80ea6ebc5b8e318 (patch)
treebe050c259ea5bfc41731ac0581df4f57034cb7a3 /net/sched/sch_api.c
parent09a8f03197d4799bc9969b35240e5606c026ded6 (diff)
downloadop-kernel-dev-8a8e3d84b1719a56f9151909e80ea6ebc5b8e318.zip
op-kernel-dev-8a8e3d84b1719a56f9151909e80ea6ebc5b8e318.tar.gz
net_sched: restore "linklayer atm" handling
commit 56b765b79 ("htb: improved accuracy at high rates") broke the "linklayer atm" handling. tc class add ... htb rate X ceil Y linklayer atm The linklayer setting is implemented by modifying the rate table which is send to the kernel. No direct parameter were transferred to the kernel indicating the linklayer setting. The commit 56b765b79 ("htb: improved accuracy at high rates") removed the use of the rate table system. To keep compatible with older iproute2 utils, this patch detects the linklayer by parsing the rate table. It also supports future versions of iproute2 to send this linklayer parameter to the kernel directly. This is done by using the __reserved field in struct tc_ratespec, to convey the choosen linklayer option, but only using the lower 4 bits of this field. Linklayer detection is limited to speeds below 100Mbit/s, because at high rates the rtab is gets too inaccurate, so bad that several fields contain the same values, this resembling the ATM detect. Fields even start to contain "0" time to send, e.g. at 1000Mbit/s sending a 96 bytes packet cost "0", thus the rtab have been more broken than we first realized. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_api.c')
-rw-r--r--net/sched/sch_api.c41
1 files changed, 41 insertions, 0 deletions
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 281c1bd..51b968d 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -285,6 +285,45 @@ static struct Qdisc_ops *qdisc_lookup_ops(struct nlattr *kind)
return q;
}
+/* The linklayer setting were not transferred from iproute2, in older
+ * versions, and the rate tables lookup systems have been dropped in
+ * the kernel. To keep backward compatible with older iproute2 tc
+ * utils, we detect the linklayer setting by detecting if the rate
+ * table were modified.
+ *
+ * For linklayer ATM table entries, the rate table will be aligned to
+ * 48 bytes, thus some table entries will contain the same value. The
+ * mpu (min packet unit) is also encoded into the old rate table, thus
+ * starting from the mpu, we find low and high table entries for
+ * mapping this cell. If these entries contain the same value, when
+ * the rate tables have been modified for linklayer ATM.
+ *
+ * This is done by rounding mpu to the nearest 48 bytes cell/entry,
+ * and then roundup to the next cell, calc the table entry one below,
+ * and compare.
+ */
+static __u8 __detect_linklayer(struct tc_ratespec *r, __u32 *rtab)
+{
+ int low = roundup(r->mpu, 48);
+ int high = roundup(low+1, 48);
+ int cell_low = low >> r->cell_log;
+ int cell_high = (high >> r->cell_log) - 1;
+
+ /* rtab is too inaccurate at rates > 100Mbit/s */
+ if ((r->rate > (100000000/8)) || (rtab[0] == 0)) {
+ pr_debug("TC linklayer: Giving up ATM detection\n");
+ return TC_LINKLAYER_ETHERNET;
+ }
+
+ if ((cell_high > cell_low) && (cell_high < 256)
+ && (rtab[cell_low] == rtab[cell_high])) {
+ pr_debug("TC linklayer: Detected ATM, low(%d)=high(%d)=%u\n",
+ cell_low, cell_high, rtab[cell_high]);
+ return TC_LINKLAYER_ATM;
+ }
+ return TC_LINKLAYER_ETHERNET;
+}
+
static struct qdisc_rate_table *qdisc_rtab_list;
struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r, struct nlattr *tab)
@@ -308,6 +347,8 @@ struct qdisc_rate_table *qdisc_get_rtab(struct tc_ratespec *r, struct nlattr *ta
rtab->rate = *r;
rtab->refcnt = 1;
memcpy(rtab->data, nla_data(tab), 1024);
+ if (r->linklayer == TC_LINKLAYER_UNAWARE)
+ r->linklayer = __detect_linklayer(r, rtab->data);
rtab->next = qdisc_rtab_list;
qdisc_rtab_list = rtab;
}
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