tso硬件分片是头部拷贝问题

最新推荐文章于 2024-08-17 14:19:28 发布

原创最新推荐文章于 2024-08-17 14:19:28 发布 · 983 阅读

1 ·

CC 4.0 BY-SA版权

linux TCP协议同时被 2 个专栏收录

35 篇文章

订阅专栏

linux Qos

1 篇文章

订阅专栏

本文详细介绍了e1000网卡驱动中TSO分片机制的具体实现过程，包括如何计算头部偏移量、设置上下文描述符及缓冲区信息等关键步骤，并展示了硬件如何根据这些信息进行数据分片。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

//skb->date指向了二层头部地址，下面是计算以太网头 + IP头大小

static inline int skb_transport_offset(const struct sk_buff *skb)

{
return skb_transport_header(skb) - skb->data;
}

static int e1000_tso(struct e1000_adapter *adapter,

struct e1000_tx_ring *tx_ring, struct sk_buff *skb,
__be16 protocol)
{
struct e1000_context_desc *context_desc;
struct e1000_buffer *buffer_info;
unsigned int i;
u32 cmd_length = 0;
u16 ipcse = 0, tucse, mss;
u8 ipcss, ipcso, tucss, tucso, hdr_len;
int err;

if (skb_is_gso(skb)) {
if (skb_header_cloned(skb)) {
err = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
if (err)
return err;
}

//hdr_len = 以太网头部 + IP 头部 + TCP 头部

hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);

//MSS大小

mss = skb_shinfo(skb)->gso_size;

if (protocol == htons(ETH_P_IP)) {
struct iphdr *iph = ip_hdr(skb);
iph->tot_len = 0;
iph->check = 0;
tcp_hdr(skb)->check = ~csum_tcpudp_magic(iph->saddr,
iph->daddr, 0,
IPPROTO_TCP,
0);
cmd_length = E1000_TXD_CMD_IP;
ipcse = skb_transport_offset(skb) - 1;
} else if (skb_is_gso_v6(skb)) {
ipv6_hdr(skb)->payload_len = 0;
tcp_hdr(skb)->check =
~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
&ipv6_hdr(skb)->daddr,
0, IPPROTO_TCP, 0);
ipcse = 0;
}
ipcss = skb_network_offset(skb);
ipcso = (void *)&(ip_hdr(skb)->check) - (void *)skb->data;
tucss = skb_transport_offset(skb);
tucso = (void *)&(tcp_hdr(skb)->check) - (void *)skb->data;
tucse = 0;

cmd_length |= (E1000_TXD_CMD_DEXT | E1000_TXD_CMD_TSE |
E1000_TXD_CMD_TCP | (skb->len - (hdr_len)));

i = tx_ring->next_to_use;
context_desc = E1000_CONTEXT_DESC(*tx_ring, i);
buffer_info = &tx_ring->buffer_info[i];

context_desc->lower_setup.ip_fields.ipcss = ipcss;
context_desc->lower_setup.ip_fields.ipcso = ipcso;
context_desc->lower_setup.ip_fields.ipcse = cpu_to_le16(ipcse);
context_desc->upper_setup.tcp_fields.tucss = tucss;
context_desc->upper_setup.tcp_fields.tucso = tucso;

context_desc->upper_setup.tcp_fields.tucse = cpu_to_le16(tucse);

//硬件分片使用的分片基础信息

//网卡硬件分片是需要硬件自动拷贝头部，考多少数据，从哪里开始考？

//拷贝的是以太网头部数据 + IP头部数据 + TCP头部（代码流程走到这里已经构建了以太网头部）

//网卡按照MSS切片数据，也就是纯数据部分为MSS大小

//所以网卡分片是从以太网头部开始拷贝的

//但是因为数据部分有变化所以网卡必须同时支持硬件校验

context_desc->tcp_seg_setup.fields.mss = cpu_to_le16(mss);

context_desc->tcp_seg_setup.fields.hdr_len = hdr_len;

context_desc->cmd_and_length = cpu_to_le32(cmd_length);

buffer_info->time_stamp = jiffies;
buffer_info->next_to_watch = i;

if (++i == tx_ring->count) i = 0;
tx_ring->next_to_use = i;

return true;
}
return false;
}