ioctl Operations

ioctl Function

Interface Configuration  Netstat, ifconfig command 에서 사용

ARP Caching and Routing Table Operations  ARP(Address Resolution Protocol) cache operations  ARP: protocol(IP) address  hardware address  Routing table operations

fcntl Function  Set socket for nonblocking I/O: F_SETFL, O_NONBLOCK  Set socket for signal-driven I/O: F_SETFL, O_ASYNC  Set socket owner: F_SETOWN  Get socket owner: F_GETOWN

Fcntl, ioctl, and routing socket

Nonblocking I/O

Blocking and Nonblocking Sockets OperationBlockingNonblocking Input TCP no data available in socket receive buffer Returns immediately with error of EWOULDBLOCK UDP socket receive buffer is empty Output TCP no room in socket send buffer immediate error return if no room in socket send buffer, or returns # of bytes written if some room in socket send buffer UDP never blocks (no actual UDP socket send buffer) never blocks (Returns # of bytes written) accept() new connection is not available Returns immediately with error of EWOULDBLOCK connec t() TCP blocks for at least RTT Returns immediately with error of EINPROGRESS if connection not established, or returns OK(==0) if connection established immediately UDP never blocks (just store peer’s IP addr/port #)

Buffering for Nonblocking Read/Write Send buffer Receive buffer

Nonblocking str_cli nonblock/strclinonb.c:

Time Line of Nonblocking Example

A Simpler Version of str_cli using concurrent processes

A Simpler Version of str_cli using Threads

Clock Time Comparison of str_cli  Sample case  input file of 2000 lines  175msec RTT  Stop-and wait:354.0 sec  select and blocking I/O: 12.3 sec  Nonblocking I/O: 6.9 sec  Two processes with fork: 8.7 sec  Threaded version: 8.5 sec 1 Simpler is better

Nonblocking connect  Usage  overlap other processing with three-way handshake(for RTT)  establish multiple connections: popular with Web browsers  shorten timeout for connection establishment(typically 75 sec)  by using select with time limit specification  Non blocking connect  Returns immediately with an error of EINPROGRESS, but TCP three-way handshake continues  check for either successful or unsuccessful completion of connection establishment using select  If server is on the same host, connection establishment normally takes place immediately(returns 0)  Many portability problems

Nonblocking Connect: Daytime Client lib/connect_nonb.c Shorten timeout

Nonblocking Multiple Connections: Web Client  Establish a connection for reading a page  Then, establish multiple connections for reading references in the page  Using nonblocking connections  Or using thread per connection

Nonblocking accept  Use nonblocking accept  Or, select for listening socket(may blocked) then, accept when listening socket is ready

Signal-Driven I/O

2 different ways to build a UDP server

Signal-Driven I/O for Sockets  Steps for Signal-driven I/O  establish SIGIO signal handler  set socket owner for receiving signals  fcntl(sockfd, F_SETOWN, getpid());  enable socket to signal-driven I/O  ioctl(sockfd, FIOASYNC, &on); /* signal-driven I/O */  ioctl(sockfd, FIONBIO, &on); /* non-blocking I/O */  SIGIO signal is generated whenever  for UDP socket  a datagram arrives  an asynchronous error occurs  for TCP sockets  Signal is generated too often  not useful  too many cases

UDP Echo Server using SIGIO (I) sigio/dgecho01.c

UDP Echo Server using SIGIO (II)