TheAnalysisofTCPprocessflowinthelinuxSystem.docVIP

The Analysis of TCP process flow in the linux System The important structure in the process We already know the TCP/IP four layer in the Internet module,so we do the sort depending on the TCP/IP four layer structure. TCP/IP The Important structure Note Physical Layer/ socket Data link Layer Socket Network Layer sock Transport Layer tcp_sock、udp_sock List 1 For Example: struct tcp_sock { /* inet_connection_sock has to be the first member of tcp_sock */ struct inet_connection_sock inet_conn; u16 tcp_header_len; /* Bytes of tcp header to send */ u16 xmit_size_goal_segs; /* Goal for segmenting output packets */ /* * Header prediction flags * 0x5?10 16 + snd_wnd in net byte order */ __be32 pred_flags; /* * RFC793 variables by their proper names. This means you can * read the code and the spec side by side (and laugh ...) * See RFC793 and RFC1122. The RFC writes these in capitals. */ u32 rcv_nxt; /* What we want to receive next */ u32 copied_seq; /* Head of yet unread data */ u32 rcv_wup; /* rcv_nxt on last window update sent */ u32 snd_nxt; /* Next sequence we send */ u32 snd_una; /* First byte we want an ack for */ u32 snd_sml; /* Last byte of the most recently transmitted small packet */ u32 rcv_tstamp; /* timestamp of last received ACK (for keepalives) */ u32 lsndtime; /* timestamp of last sent data packet (for restart window) */ /* Data for direct copy to user */ struct { struct sk_buff_head prequeue; struct task_struct *task; struct iovec *iov; int memory; int len; #ifdef CONFIG_NET_DMA /* members for async copy */ struct dma_chan *dma_chan; int wakeup; struct dma_pinned_list *pinned_list; dma_cookie_t dma_cookie; #endif } ucopy; u32 snd_wl1; /* Sequence for window update */ u32 snd_wnd; /* The window we expect to receive */ u32 max_window; /* Maximal window ever seen from peer */ u32 mss_cache; /* Cached effective mss, not including SACKS */ u32 window_clamp; /* Maximal window to advertise