Functions to modify

• INTERCEPTING TCP RETRANSMISSIONS

  • Timeout based retransmit - tcp_timer.c:344 - *void tcp_retransmit_timer(struct sock sk) Intercept this function, set state and call again later in callback
  • Fast retransmit - tcp_output.c:2505 - *void tcp_xmit_retransmit_queue(struct sock sk) Intercept this, set state and call again in callback

• tcp_output.c:852 - tcp_transmit_skb - sock, sk_buff, clone_it, gfp_mask

  • Intercept this function to make it deadline aware

• Important functions

  • sock.c:2390 - void sock_init_data(struct socket *sock, struct sock *sk)
  • sock.c:1504 - void sk_free(struct sock *sk)
  • sock.c:986 - int sock_setsockopt(struct socket *sock, int level, int optname, char __user *optval, unsigned int optlen)

• Add locks and intercept here:

  • tcp_output.c:2511 - void tcp_xmit_retransmit_queue(struct sock *sk)
  • tcp_output.c:1852 - static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, int push_one, gfp_t gfp)

• Resources

  • Kernel atomic types - http://www.makelinux.net/books/lkd2/ch09lev1sec1
  • Kernel GDB - http://elinux.org/Debugging_The_Linux_Kernel_Using_Gdb
  • Kernel timers - http://www.ibm.com/developerworks/library/l-timers-list/
  • More about timers - http://www.makelinux.net/ldd3/chp-7-sect-4
  • TCP Output Handling
  • TCP Socket Bufs
  • Linux IP Networking
  • Linux network stack - http://www.cubrid.org/blog/dev-platform/understanding-tcp-ip-network-stack/

• Papers

  • An Evaluation of Network Stack Parallelization Strategies in Modern Operating Systems - https://www.usenix.org/legacy/event/usenix06/tech/full_papers/willmann/willmann_html/Paper_html.html