Network Applications

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Network Applications
user
kernel
BSD Sockets
socket
INET Sockets
sock
sk_buff
TCP
UDP
IP
ARP
PPP
SLIP
Ethernet
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sys_socketcall()
send
ip_queue_xmit
sys_send()
sock-gtops-gtsendmsg
dev_queue_xmit
inet_sendmsg()
do_dev_queue_xmit
sk-gtprot-gtsendmsg
tcp_sendmsg()
dev-gthard_start_xmit
el3_start_xmit()
do_tcp_sendmsg()
tcp_send_skb
sk-gtprot-gtqueue_xmit
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(No Transcript)
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do_tcp_sendmsg()

• Allocate sk_buff
• construct hardware and IP header
• sk-gtprot-gtbuild_header()
• ip_build_header
• construct TCP header

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ip_queue_xmit()

• Partially initialize skb (sk_buff)
• check free value
• free 1 dont free, keep skb on the sk send
  list
• free 0 after device send out, it will be
  freed
• compute checksum
• if lookback call ip_lookback()
• if fragmentation call if_fragment()
• call dev_queue_xmit()

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do_dev_queue_xmit()

• Lock device
• check if transmission
• find the corresponding list
• queue the skb in the tail of list
• dequeue the first skb in the list and call the
  dev-gthard_start_xmit()

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el3_interrupt()
tcp_rcv
el3_rx()
tcp_data()
netif_rx()
tcp_queue()
sk-gtdata_ready()
net_bh()
def_callback2()
pt_prev-gtfun()
ip_rcv()
ipprot-gthandler()
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Function Illustration

• el3_interrupt()
• get the device interface
• call el3_rx()
• el3_rx()
• allocate sk_buff
• determine the packets protocol ID
• call netif_rx()

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Function Illustration (Cont.)

• netif_rx()
• check if backlog_size is appropriate
• if no gt drop
• else enqueue in the system backlog list
• call mark_bh()

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Function Illustration (Cont.)

• net_bh()
• dev_transmit() check each network interface if
  anyone is ready to transmit
• _sbk_unlink() dequeue the sk_buff from the
  backlog list
• search the two system list for packet type
• ptype_all ETH_P_ALL
• ptype_base main protocol list
• call pt_prev-gtfunc() i.e. ip_rcv()

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Function Illustration (Cont.)

• ip_rcv()
• correction checking
• ip_options_compile ip options preprocessing
• ip_defrag()
• if my packet
• ip_option_processing
• check if raw ip
• find the protocol and call ipprot-gthandler()
  tcp_rcv()
• else ip_forward()

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Function Illustration (Cont.)

• tcp_rcv()
• _tcp_v4_lookup() find the upper INET sock
  structure
• call tcp_data()
• tcp_data()
• handle the data
• call tcp_queue

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Function Illustration (Cont.)

• tcp_queue()
• tcp_insert_skb() add a sk_buff to the tcp
  receive queue (sk-gtreceive_queue)
• sk-gtdata_ready() def_callback2()
• def_callback2()
• wake up the sleeping process

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sys_socketcall()
sys_recv()
inet_recvmsg()
tcp_recvmsg()