[PATCH 1/1] tc: custom qdisc pkt size translation table

Added the "custom" linklayer qdisc stab option.
This allows the user to specify the pkt size translation
parameters from stdin.
Example:
   tc qdisc add ... stab tsize 8 linklayer custom htb
   Custom size table:
   InputSizeStart -> IntputSizeEnd: Output Pkt Size
   0 - 255: 400
   256 - 511: 800
   512 - 767: 1200
   768 - 1023: 1600
   1024 - 1279: 2000
   1280 - 1535: 2400
   1536 - 1791: 2800
   1792 - 2047: 3200

Signed-off-by: McCabe, Robert J <redacted>
---
 include/linux/pkt_sched.h |  1 +
 tc/tc_core.c              | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 tc/tc_core.h              |  2 +-
 tc/tc_stab.c              |  4 +++-
 tc/tc_util.c              |  5 +++++
 5 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index 099bf55..289bb81 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h

@@ -82,6 +82,7 @@ enum tc_link_layer {
 	TC_LINKLAYER_UNAWARE, /* Indicate unaware old iproute2 util */
 	TC_LINKLAYER_ETHERNET,
 	TC_LINKLAYER_ATM,
+	TC_LINKLAYER_CUSTOM,
 };
 #define TC_LINKLAYER_MASK 0x0F /* limit use to lower 4 bits */
 

diff --git a/tc/tc_core.c b/tc/tc_core.c
index 821b741..fb04704 100644
--- a/tc/tc_core.c
+++ b/tc/tc_core.c

@@ -21,6 +21,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <string.h>
+#include <assert.h>
 
 #include "tc_core.h"
 #include <linux/atm.h>

@@ -28,6 +29,16 @@
 static double tick_in_usec = 1;
 static double clock_factor = 1;
 
+struct size_table_entry {
+	unsigned int input_size_boundary_start;
+	unsigned int output_size_bytes;
+};
+
+//TODO: free
+static struct size_table_entry* custom_size_table = NULL;
+static int num_size_table_entries = 0;
+
+
 int tc_core_time2big(unsigned int time)
 {
 	__u64 t = time;

@@ -89,6 +100,23 @@ static unsigned int tc_align_to_atm(unsigned int size)
 	return linksize;
 }
 
+static unsigned int tc_align_to_custom(unsigned int size)
+{
+	int i;
+
+	assert(custom_size_table != NULL);
+
+	for(i = num_size_table_entries -1; i >= 0 ; --i)
+	{
+		if(custom_size_table[i].input_size_boundary_start < size)
+		{
+			/* found it */
+			return custom_size_table[i].output_size_bytes;
+		}
+	}
+	return 0;
+}
+
 static unsigned int tc_adjust_size(unsigned int sz, unsigned int mpu, enum link_layer linklayer)
 {
 	if (sz < mpu)

@@ -97,6 +125,8 @@ static unsigned int tc_adjust_size(unsigned int sz, unsigned int mpu, enum link_
 	switch (linklayer) {
 	case LINKLAYER_ATM:
 		return tc_align_to_atm(sz);
+	case LINKLAYER_CUSTOM:
+		return tc_align_to_custom(sz);
 	case LINKLAYER_ETHERNET:
 	default:
 		/* No size adjustments on Ethernet */

@@ -185,6 +215,27 @@ int tc_calc_size_table(struct tc_sizespec *s, __u16 **stab)
 	if (!*stab)
 		return -1;
 
+	if(LINKLAYER_CUSTOM == linklayer)
+	{
+		custom_size_table = malloc(sizeof(struct size_table_entry)* s->tsize);
+		if(!custom_size_table)
+			return -1;
+		num_size_table_entries = s->tsize;
+
+		printf("Custom size table:\n");
+		printf("InputSizeStart -> IntputSizeEnd : Output Pkt Size\n");
+		for(i = 0; i <= s->tsize - 1; ++i)
+		{
+			printf("%d - %d: ", i << s->cell_log, ((i+1) << s->cell_log) - 1);
+			if(!scanf("%u", &custom_size_table[i].output_size_bytes))
+			{
+				fprintf(stderr, "Invalid custom stab table entry!\n");
+				return -1;
+			}
+
+			custom_size_table[i].input_size_boundary_start = i << s->cell_log;
+		}
+	}
 again:
 	for (i = s->tsize - 1; i >= 0; i--) {
 		sz = tc_adjust_size((i + 1) << s->cell_log, s->mpu, linklayer);

diff --git a/tc/tc_core.h b/tc/tc_core.h
index 8a63b79..8e97222 100644
--- a/tc/tc_core.h
+++ b/tc/tc_core.h

@@ -10,9 +10,9 @@ enum link_layer {
 	LINKLAYER_UNSPEC,
 	LINKLAYER_ETHERNET,
 	LINKLAYER_ATM,
+	LINKLAYER_CUSTOM,
 };
 
-
 int  tc_core_time2big(unsigned time);
 unsigned tc_core_time2tick(unsigned time);
 unsigned tc_core_tick2time(unsigned tick);

diff --git a/tc/tc_stab.c b/tc/tc_stab.c
index 1a0a3e3..8374c76 100644
--- a/tc/tc_stab.c
+++ b/tc/tc_stab.c

@@ -37,7 +37,9 @@ static void stab_help(void)
 		"   tsize     : how many slots should size table have {512}\n"
 		"   mpu       : minimum packet size used in rate computations\n"
 		"   overhead  : per-packet size overhead used in rate computations\n"
-		"   linklayer : adapting to a linklayer e.g. atm\n"
+		"   linklayer : adapting to a linklayer e.g. ethernet, atm or custom\n"
+		"               a \"custom\" linklayer reads size table entries from\n"
+		"               stdin\n"
 		"Example: ... stab overhead 20 linklayer atm\n");
 
 }

diff --git a/tc/tc_util.c b/tc/tc_util.c
index 24ca1f1..3ee1098 100644
--- a/tc/tc_util.c
+++ b/tc/tc_util.c

@@ -485,6 +485,8 @@ int get_linklayer(unsigned int *val, const char *arg)
 		res = LINKLAYER_ATM;
 	else if (matches(arg, "adsl") == 0)
 		res = LINKLAYER_ATM;
+	else if (matches(arg, "custom") == 0)
+		res = LINKLAYER_CUSTOM;
 	else
 		return -1; /* Indicate error */
 

@@ -504,6 +506,9 @@ void print_linklayer(char *buf, int len, unsigned int linklayer)
 	case LINKLAYER_ATM:
 		snprintf(buf, len, "%s", "atm");
 		return;
+	case LINKLAYER_CUSTOM:
+		snprintf(buf, len, "%s", "custom");
+		return;
 	default:
 		snprintf(buf, len, "%s", "unknown");
 		return;

-- 
2.7.4

On Tue, 2017-06-27 at 11:29 -0500, McCabe, Robert J wrote:

You can not do this : This file is coming from the kernel
( include/uapi/linux/pkt_sched.h )

Since your patch is user space only, you need to find another way ?

Yeah, sorry didn't even think about that.
I guess my first question would be is there another way via the
iproute2 project where a user could
configure the stab->data pkt size translation table used in the
__qdisc_calculate_pkt_len method
in the kernel source (net/sched/sched_api.c)?

Also, let's say I went ahead and made the added TC_LINK_LAYER_CUSTOM
to the include/uapi/linux/pkt_sched.h
file in the kernel source ... would I also need to make the same
change in include/uapi/linux/pkt_sched.h in
the iproute2 source?

Do you recommend an alternative (more elegant) approach to what I'm
trying to accomplish?


On Tue, Jun 27, 2017 at 11:55 AM, Eric Dumazet [off-list ref] wrote:

On Tue, 2017-06-27 at 11:29 -0500, McCabe, Robert J wrote:

quoted

Added the "custom" linklayer qdisc stab option.
This allows the user to specify the pkt size translation
parameters from stdin.
Example:
   tc qdisc add ... stab tsize 8 linklayer custom htb
   Custom size table:
   InputSizeStart -> IntputSizeEnd: Output Pkt Size
   0 - 255: 400
   256 - 511: 800
   512 - 767: 1200
   768 - 1023: 1600
   1024 - 1279: 2000
   1280 - 1535: 2400
   1536 - 1791: 2800
   1792 - 2047: 3200

Signed-off-by: McCabe, Robert J <redacted>
---
 include/linux/pkt_sched.h |  1 +
 tc/tc_core.c              | 51 +++++++++++++++++++++++++++++++++++++++++++++++
 tc/tc_core.h              |  2 +-
 tc/tc_stab.c              |  4 +++-
 tc/tc_util.c              |  5 +++++
 5 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
index 099bf55..289bb81 100644
--- a/include/linux/pkt_sched.h
+++ b/include/linux/pkt_sched.h

@@ -82,6 +82,7 @@ enum tc_link_layer {
      TC_LINKLAYER_UNAWARE, /* Indicate unaware old iproute2 util */
      TC_LINKLAYER_ETHERNET,
      TC_LINKLAYER_ATM,
+     TC_LINKLAYER_CUSTOM,
 };
 #define TC_LINKLAYER_MASK 0x0F /* limit use to lower 4 bits */

You can not do this : This file is coming from the kernel
( include/uapi/linux/pkt_sched.h )

Since your patch is user space only, you need to find another way ?

On Tue, 2017-06-27 at 12:37 -0500, Robert McCabe wrote:

Yeah, sorry didn't even think about that.
I guess my first question would be is there another way via the
iproute2 project where a user could
configure the stab->data pkt size translation table used in the
__qdisc_calculate_pkt_len method
in the kernel source (net/sched/sched_api.c)?

Also, let's say I went ahead and made the added TC_LINK_LAYER_CUSTOM
to the include/uapi/linux/pkt_sched.h
file in the kernel source ... would I also need to make the same
change in include/uapi/linux/pkt_sched.h in
the iproute2 source?

Do you recommend an alternative (more elegant) approach to what I'm
trying to accomplish?

Note that since you probably want to be able to dump the table
(tc -s -d qdisc show ), you might need a kernel change anyway.

Then the iproute2 change would be a companion.