Linux IP stack on kernel 2.4.18

Hi All,

I'm using kernel 2.4.18 and developing an ethernet network interface driver.
I have two problems that if you may consult me how to solve them -

1.. How can I adjust the throttling parameter of the IP stack not to drop any packet ? Meantime the IP stack routes 55k packets/sec and all the other it just drops (I can see them by the result of netif_rx).
2.. Routing jumbo packets through IP stack - I send 9K packets in size and IP stack routes the packets but by sending 1K packets in size ! is this possible ? I tripple checked the device driver on receive and transmit and it's ok. Do you know what is the problem ?


Thank you alot,
Rabeeh

--snip/snip

2.. Routing jumbo packets through IP stack - I send 9K packets in size and IP stack routes the packets but by sending 1K packets in size ! is this possible ? I tripple checked the device driver on receive and transmit and it's ok. Do you know what is the problem ?

did you check you MTU?

	tm

-- 
in some way i do, and in some way i don't.

Thomas 'Dent' Mirlacher wrote:

--snip/snip

 

quoted

2.. Routing jumbo packets through IP stack - I send 9K packets in size and IP stack routes the packets but by sending 1K packets in size ! is this possible ? I tripple checked the device driver on receive and transmit and it's ok. Do you know what is the problem ?
   

did you check you MTU?

sh-2.04# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 64:41:40:12:12:31 
          inet addr:10.2.40.130  Bcast:10.2.255.255  Mask:255.255.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:9700  Metric:1
          RX packets:5668 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3280 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:4787563 (4.5 Mb)  TX bytes:543741 (530.9 Kb)
          Interrupt:32

tm

 

I fixed the problems. I'm replying for the record of the mailing list.

Rabeeh Khoury wrote:

Hi All,

I'm using kernel 2.4.18 and developing an ethernet network interface 
driver.
I have two problems that if you may consult me how to solve them -

1.. How can I adjust the throttling parameter of the IP stack not to 
drop any packet ? Meantime the IP stack routes 55k packets/sec and all 
the other it just drops (I can see them by the result of netif_rx). 

echo 50000 > /proc/sys/net/core/netdev_max_backlog

This puts the throttling parameter of the IP stack to 50000, instead of 
300 which is the defaul in kernel 2.4.18 (the default is set in 
net/core/dev.c with the variable 'int netdev_max_backlog = 300;')

2.. Routing jumbo packets through IP stack - I send 9K packets in size 
and IP stack routes the packets but by sending 1K packets in size ! is 
this possible ? I tripple checked the device driver on receive and 
transmit and it's ok. Do you know what is the problem ? 

The HW I'v used that generates jumbo packets has put a wrong 
total_length field in the IP header, which made IP stack remove a large 
chunck of the packet. The relevant code that removes the chunck is in 
net/ipv4/ip_input.c -

                /* Our transport medium may have padded the buffer out. 
Now we know it
                 * is IP we can trim to the true length of the frame.
                 * Note this now means skb->len holds ntohs(iph->tot_len).
                 */
                if (skb->len > len) {
                      __pskb_trim(skb, len);
                        if (skb->ip_summed == CHECKSUM_HW)
                                skb->ip_summed = CHECKSUM_NONE;
                }

Thank you alot,
Rabeeh

I fixed the problems. I'm replying for the record of the mailing list.

Rabeeh Khoury wrote:

Hi All,

I'm using kernel 2.4.18 and developing an ethernet network interface 
driver.
I have two problems that if you may consult me how to solve them -

1.. How can I adjust the throttling parameter of the IP stack not to 
drop any packet ? Meantime the IP stack routes 55k packets/sec and all 
the other it just drops (I can see them by the result of netif_rx). 

echo 50000 > /proc/sys/net/core/netdev_max_backlog

This puts the throttling parameter of the IP stack to 50000, instead of 
300 which is the defaul in kernel 2.4.18 (the default is set in 
net/core/dev.c with the variable 'int netdev_max_backlog = 300;')

2.. Routing jumbo packets through IP stack - I send 9K packets in size 
and IP stack routes the packets but by sending 1K packets in size ! is 
this possible ? I tripple checked the device driver on receive and 
transmit and it's ok. Do you know what is the problem ? 

The HW I'v used that generates jumbo packets has put a wrong 
total_length field in the IP header, which made IP stack remove a large 
chunck of the packet. The relevant code that removes the chunck is in 
net/ipv4/ip_input.c -

                /* Our transport medium may have padded the buffer out. 
Now we know it
                 * is IP we can trim to the true length of the frame.
                 * Note this now means skb->len holds ntohs(iph->tot_len).
                 */
                if (skb->len > len) {
                      __pskb_trim(skb, len);
                        if (skb->ip_summed == CHECKSUM_HW)
                                skb->ip_summed = CHECKSUM_NONE;
                }

Thank you alot,
Rabeeh

Rabeeh Khoury writes:
 > 
 > 1.. How can I adjust the throttling parameter of the IP stack not to drop any packet ? Meantime the IP stack routes 55k packets/sec and all the other it just drops (I can see them by the result of netif_rx).

 Hello!

 There are no "throttling parameter" you have probably hit some of your 
 machine limits, bandwidth, CPU etc and 55 kpps can be decent. You didn't 
 mention your input rate, paket size or hardware.

 http://www.cyberus.ca/~hadi/usenix-paper.tgz

 Discusses related issues..


 Cheers.
						--ro