Re: tulip and VLAN tagging - accepting larger frames without affecting higher layers?

From: Paul P Komkoff Jr (i@stingr.net)
Date: Thu Apr 11 2002 - 10:23:27 EST

Replying to Marc Haber:
> Hi,
>
> VLAN-Tagging on Linux seems still to be problematic, despite the dot1q
> patch being in the kernel since a few months. Problems arise when a
> system running on an untagged switch port sends a frame using full MTU
> to a system that runs VLAN tagging. The switch adds the VLAN tag to
> the frame which then exceeds the MTU and is then dropped by the
> receiving Linux system.

You can take latest stable linux-stingr kernel from
bk://linux-stingr.bkbits.net/stable4

It contains (following) (rediffed) working tulip mtu patch :)

diff -urN linux-2.4.9-ac10-novlan/drivers/net/tulip/interrupt.c linux-2.4.9-ac10/drivers/net/tulip/interrupt.c
--- linux-2.4.9-ac10-novlan/drivers/net/tulip/interrupt.c Wed Jun 20 22:15:44 2001
+++ linux-2.4.9-ac10/drivers/net/tulip/interrupt.c Mon Sep 10 18:44:12 2001
@@ -128,8 +128,8 @@
                                    dev->name, entry, status);
                 if (--rx_work_limit < 0)
                         break;
- if ((status & 0x38008300) != 0x0300) {
- if ((status & 0x38000300) != 0x0300) {
+ if ((status & (0x38000000 | RxDescFatalErr | RxWholePkt)) != RxWholePkt) {
+ if ((status & (0x38000000 | RxWholePkt)) != RxWholePkt) {
                                 /* Ingore earlier buffers. */
                                 if ((status & 0xffff) != 0x7fff) {
                                         if (tulip_debug > 1)
@@ -155,10 +155,10 @@
                         struct sk_buff *skb;
 
 #ifndef final_version
- if (pkt_len > 1518) {
+ if (pkt_len > 1522) {
                                 printk(KERN_WARNING "%s: Bogus packet size of %d (%#x).\n",
                                            dev->name, pkt_len, pkt_len);
- pkt_len = 1518;
+ pkt_len = 1522;
                                 tp->stats.rx_length_errors++;
                         }
 #endif
diff -urN linux-2.4.9-ac10-novlan/drivers/net/tulip/tulip.h linux-2.4.9-ac10/drivers/net/tulip/tulip.h
--- linux-2.4.9-ac10-novlan/drivers/net/tulip/tulip.h Wed Jun 20 22:19:02 2001
+++ linux-2.4.9-ac10/drivers/net/tulip/tulip.h Mon Sep 10 18:42:27 2001
@@ -186,7 +186,7 @@
 
 enum desc_status_bits {
         DescOwned = 0x80000000,
- RxDescFatalErr = 0x8000,
+ RxDescFatalErr = 0x4842,
         RxWholePkt = 0x0300,
 };
 
@@ -264,7 +264,7 @@
 
 #define MEDIA_MASK 31
 
-#define PKT_BUF_SZ 1536 /* Size of each temporary Rx buffer. */
+#define PKT_BUF_SZ 1540 /* Size of each temporary Rx buffer. */
 
 #define TULIP_MIN_CACHE_LINE 8 /* in units of 32-bit words */
 
diff -urN linux-2.4.9-ac10-novlan/drivers/net/tulip/tulip_core.c linux-2.4.9-ac10/drivers/net/tulip/tulip_core.c
--- linux-2.4.9-ac10-novlan/drivers/net/tulip/tulip_core.c Mon Sep 10 18:50:47 2001
+++ linux-2.4.9-ac10/drivers/net/tulip/tulip_core.c Mon Sep 10 18:39:59 2001
@@ -59,7 +59,7 @@
 #if defined(__alpha__) || defined(__arm__) || defined(__hppa__) \
         || defined(__sparc_) || defined(__ia64__) \
         || defined(__sh__) || defined(__mips__)
-static int rx_copybreak = 1518;
+static int rx_copybreak = 1522;
 #else
 static int rx_copybreak = 100;
 #endif 

-- 
Paul P 'Stingray' Komkoff 'Greatest' Jr // (icq)23200764 // (irc)Spacebar
  PPKJ1-RIPE // (smtp)i@stingr.net // (http)stingr.net // (pgp)0xA4B4ECA4
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This archive was generated by hypermail 2b29 : Mon Apr 15 2002 - 22:00:19 EST