From: Raimonds Cicans <ray@apollo.lv>
To: romieu@fr.zoreil.com
Cc: netdev@vger.kernel.org
Subject: r8169: Fix receive buffer length when MTU is between 1515 and 1536 (Was: r8169: fix driver drop incoming packets >= 1515 ...)
Date: Fri, 13 Nov 2009 22:52:19 +0200 [thread overview]
Message-ID: <4AFDC703.10902@apollo.lv> (raw)
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In r8169 driver MTU is used to calculate receive buffer size.
Receive buffer size is used to configure hardware incoming packet filter.
For jumbo frames:
Receive buffer size = Max frame size = MTU + 14 (ethernet header) + 4
(vlan header) + 4 (ethernet checksum) = MTU + 22
Bug:
driver for all MTU up to 1536 use receive buffer size 1536
As you can see from formula, this mean all IP packets > 1536 - 22
(for vlan tagged, 1536 - 18 for not tagged) are dropped by hardware
filter.
Example:
host_good> ifconfig eth0 mtu 1536
host_r8169> ifconfig eth0 mtu 1536
host_good> ping host_r8169
Ok
host_good> ping -s 1500 host_r8169
Fail
host_good> ifconfig eth0 mtu 7000
host_r8169> ifconfig eth0 mtu 7000
host_good> ping -s 1500 host_r8169
Ok
Bonus: got rid of magic number 8
Signed-off-by: Raimonds Cicans <ray@apollo.lv>
---
--- linux-2.6.31/drivers/net/r8169.c.orig 2009-11-06 21:52:12.722326601 +0200
+++ linux-2.6.31/drivers/net/r8169.c 2009-11-06 22:09:17.242224014 +0200
@@ -2229,9 +2229,9 @@ static void __devexit rtl8169_remove_one
static void rtl8169_set_rxbufsize(struct rtl8169_private *tp,
struct net_device *dev)
{
- unsigned int mtu = dev->mtu;
+ unsigned int max_frame = dev->mtu + VLAN_ETH_HLEN + ETH_FCS_LEN;
- tp->rx_buf_sz = (mtu > RX_BUF_SIZE) ? mtu + ETH_HLEN + 8 : RX_BUF_SIZE;
+ tp->rx_buf_sz = (max_frame > RX_BUF_SIZE) ? max_frame : RX_BUF_SIZE;
}
static int rtl8169_open(struct net_device *dev)
next reply other threads:[~2009-11-13 20:52 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-13 20:52 Raimonds Cicans [this message]
2009-11-14 3:59 ` r8169: Fix receive buffer length when MTU is between 1515 and 1536 David Miller
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