Patchwork [RFC] r8169 : why SG / TX checksum are default disabled

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Submitter fran├žois romieu
Date July 20, 2012, 9:01 p.m.
Message ID <20120720210107.GA28118@electric-eye.fr.zoreil.com>
Download mbox | patch
Permalink /patch/172350/
State RFC
Delegated to: David Miller
Headers show

Comments

fran├žois romieu - July 20, 2012, 9:01 p.m.
hayeswang <hayeswang@realtek.com> :
[...]
> If the hw only fills in the checksum fields of IP header, UDP header, and TCP
> header, the patch would work. However, the hw would also fill in the total
> length field of IP header, so it causes problems.

Thanks, I missed this part. The patch below should be getting better now.

Btw, would there be any point in setting the TcpHeaderOffset field for
the post-8168c chipsets ?

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hayeswang - July 24, 2012, 6:34 a.m.
Francois Romieu [mailto:romieu@fr.zoreil.com] 
> Sent: Saturday, July 21, 2012 5:01 AM
> To: Hayeswang
> Cc: 'David Miller'; eric.dumazet@gmail.com; netdev@vger.kernel.org
> Subject: Re: [RFC] r8169 : why SG / TX checksum are default disabled
> 
[...]
> 
> Btw, would there be any point in setting the TcpHeaderOffset field for
> the post-8168c chipsets ?

It is used to tell the haredware where the TCP header starts from. I think it is
reserved for ipv6.
 
Best Regards,
Hayes

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David Miller - July 24, 2012, 6:59 a.m.
From: hayeswang <hayeswang@realtek.com>
Date: Tue, 24 Jul 2012 14:34:04 +0800

>   Francois Romieu [mailto:romieu@fr.zoreil.com] 
>> Sent: Saturday, July 21, 2012 5:01 AM
>> To: Hayeswang
>> Cc: 'David Miller'; eric.dumazet@gmail.com; netdev@vger.kernel.org
>> Subject: Re: [RFC] r8169 : why SG / TX checksum are default disabled
>> 
> [...]
>> 
>> Btw, would there be any point in setting the TcpHeaderOffset field for
>> the post-8168c chipsets ?
> 
> It is used to tell the haredware where the TCP header starts from. I think it is
> reserved for ipv6.

I still have not seen a good explanation why the chip modifies fields
in the packet, such as the length, when we ask it only to compute the
checksum?
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hayeswang - July 25, 2012, 2:10 a.m.
David Miller [mailto:davem@davemloft.net] 
> Sent: Tuesday, July 24, 2012 3:00 PM
> To: Hayeswang
> Cc: romieu@fr.zoreil.com; eric.dumazet@gmail.com; 
> netdev@vger.kernel.org
> Subject: Re: [RFC] r8169 : why SG / TX checksum are default disabled
> 
[...]
> 
> I still have not seen a good explanation why the chip modifies fields
> in the packet, such as the length, when we ask it only to compute the
> checksum?

I don't know the history and the detail about the bug. I think only our designer
could answer your question. I guess it is a careless mistake.
 
Best Regards,
Hayes

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Patch

diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
index be4e00f..2420af6 100644
--- a/drivers/net/ethernet/realtek/r8169.c
+++ b/drivers/net/ethernet/realtek/r8169.c
@@ -5740,7 +5740,7 @@  err_out:
 	return -EIO;
 }
 
-static inline void rtl8169_tso_csum(struct rtl8169_private *tp,
+static inline bool rtl8169_tso_csum(struct rtl8169_private *tp,
 				    struct sk_buff *skb, u32 *opts)
 {
 	const struct rtl_tx_desc_info *info = tx_desc_info + tp->txd_version;
@@ -5753,6 +5753,15 @@  static inline void rtl8169_tso_csum(struct rtl8169_private *tp,
 	} else if (skb->ip_summed == CHECKSUM_PARTIAL) {
 		const struct iphdr *ip = ip_hdr(skb);
 
+		if (unlikely(skb->len < ETH_ZLEN &&
+		    (tp->mac_version == RTL_GIGA_MAC_VER_34))) {
+			if (skb_padto(skb, ETH_ZLEN))
+				return false;
+			skb_checksum_help(skb);
+			skb_put(skb, ETH_ZLEN - skb->len);
+			return true;
+		}
+
 		if (ip->protocol == IPPROTO_TCP)
 			opts[offset] |= info->checksum.tcp;
 		else if (ip->protocol == IPPROTO_UDP)
@@ -5760,6 +5769,7 @@  static inline void rtl8169_tso_csum(struct rtl8169_private *tp,
 		else
 			WARN_ON_ONCE(1);
 	}
+	return true;
 }
 
 static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
@@ -5783,25 +5793,26 @@  static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
 	if (unlikely(le32_to_cpu(txd->opts1) & DescOwn))
 		goto err_stop_0;
 
+	opts[1] = cpu_to_le32(rtl8169_tx_vlan_tag(tp, skb));
+	opts[0] = DescOwn;
+
+	if (!rtl8169_tso_csum(tp, skb, opts))
+		goto err_update_stats_0;
+
 	len = skb_headlen(skb);
 	mapping = dma_map_single(d, skb->data, len, DMA_TO_DEVICE);
 	if (unlikely(dma_mapping_error(d, mapping))) {
 		if (net_ratelimit())
 			netif_err(tp, drv, dev, "Failed to map TX DMA!\n");
-		goto err_dma_0;
+		goto err_free_skb_1;
 	}
 
 	tp->tx_skb[entry].len = len;
 	txd->addr = cpu_to_le64(mapping);
 
-	opts[1] = cpu_to_le32(rtl8169_tx_vlan_tag(tp, skb));
-	opts[0] = DescOwn;
-
-	rtl8169_tso_csum(tp, skb, opts);
-
 	frags = rtl8169_xmit_frags(tp, skb, opts);
 	if (frags < 0)
-		goto err_dma_1;
+		goto err_unmap_2;
 	else if (frags)
 		opts[0] |= FirstFrag;
 	else {
@@ -5849,10 +5860,11 @@  static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
 
 	return NETDEV_TX_OK;
 
-err_dma_1:
+err_unmap_2:
 	rtl8169_unmap_tx_skb(d, tp->tx_skb + entry, txd);
-err_dma_0:
+err_free_skb_1:
 	dev_kfree_skb(skb);
+err_update_stats_0:
 	dev->stats.tx_dropped++;
 	return NETDEV_TX_OK;