• William Allen Simpson's avatar
    TCPCT part 1d: define TCP cookie option, extend existing struct's · 435cf559
    William Allen Simpson authored
    Data structures are carefully composed to require minimal additions.
    For example, the struct tcp_options_received cookie_plus variable fits
    between existing 16-bit and 8-bit variables, requiring no additional
    space (taking alignment into consideration).  There are no additions to
    tcp_request_sock, and only 1 pointer in tcp_sock.
    
    This is a significantly revised implementation of an earlier (year-old)
    patch that no longer applies cleanly, with permission of the original
    author (Adam Langley):
    
        http://thread.gmane.org/gmane.linux.network/102586
    
    The principle difference is using a TCP option to carry the cookie nonce,
    instead of a user configured offset in the data.  This is more flexible and
    less subject to user configuration error.  Such a cookie option has been
    suggested for many years, and is also useful without SYN data, allowing
    several related concepts to use the same extension option.
    
        "Re: SYN floods (was: does history repeat itself?)", September 9, 1996.
        http://www.merit.net/mail.archives/nanog/1996-09/msg00235.html
    
        "Re: what a new TCP header might look like", May 12, 1998.
        ftp://ftp.isi.edu/end2end/end2end-interest-1998.mail
    
    These functions will also be used in subsequent patches that implement
    additional features.
    
    Requires:
       TCPCT part 1a: add request_values parameter for sending SYNACK
       TCPCT part 1b: generate Responder Cookie secret
       TCPCT part 1c: sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS
    
    Signed-off-by: William.Allen.Simpson@gmail.com
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    435cf559
tcp_ipv4.c 63.1 KB