请教一个关于skb的问题

sillyaboy

我从网卡的环行缓冲队列里取了一个skb,我如何判断他是那种类型的数据包呢？比如说tcp udp

Godbach

仔细看一下skb结构体。关键的是skb->data成员。他指向数据报文的头部。同时，data还是随着报文在不同的层指向不同的内容。如果报文还在链路层，那么data指向MAC，如果是网络层，指向iphdr. 能够得到报文的头部，整个报文的内容你都可以通过偏移取出来了

sillyaboy

哦·谢谢啊~！

accessory

我觉得还有个简单点的方法.
skb中有个成员叫h,就是表示header的.
下面这段来自LDD3 CHAPTER 17  PAGE 529

SKB data structure:
union { /* ... */ } h;
union { /* ... */ } nh;
union { /*... */} mac;
Pointers to the various levels of headers contained within the packet. Each field
of the union is a pointer to a different type of data structure. h hosts pointers to
transport layer headers (for example, struct tcphdr *th); nh includes network
layer headers (such as struct iphdr *iph); and mac collects pointers to link-layer
headers (such as struct ethdr *ethernet).
If your driver needs to look at the source and destination addresses of a TCP
packet, it can find them in skb->h.th. See the header file for the full set of header
types that can be accessed in this way.

Godbach

原帖由 accessory 于 2009-4-24 23:26 发表
我觉得还有个简单点的方法.
skb中有个成员叫h,就是表示header的.
下面这段来自LDD3 CHAPTER 17  PAGE 529

SKB data structure:
union { /* ... */ } h;
union { /* ... */ } nh;
union { /*... */} ma ...

这个是有条件限制的，LZ需要了解一下这几个分别在什么时候才可以使用