[lkml]   [1998]   [Dec]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: Logging unserved ports
    >My understanding is, roughly, FINs are used to close an ESTABLISHED
    >connection, which means SYN should no longer be set. If SYN (or SYN+ACK)
    >is received for a socket not yet in ESTABLISHED state, and there is no
    >listener or whatnot, RST should be sent, not FIN (nor SYN). If there are
    >conditions in which FIN+SYN is valid, please enlighten me :)

    Roughly, FIN means "I have no more data to send" and SYN means "this is the
    first packet of a new connection". It's probably valid to have SYN and FIN
    both set if you only have less than one MSS-worth of data to transmit, but
    this is a pretty unlikely circumstance to occur. I think transaction TCP
    works this way but I'm not sure.

    >This does remind me of one other question, though: is FIN+RST (w/ or w/o
    >ACK set) ever a valid combination? I tend to think not (by pretty much the

    No. RST combined with SYN or FIN isn't a sensible thing to send. A RST
    causes the connection to be immediately torn down and this is incompatible
    with either gracefully closing it or initiating a new one. :-)

    RST+ACK is valid though.


    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to
    Please read the FAQ at

     \ /
      Last update: 2005-03-22 13:46    [W:0.027 / U:38.052 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site