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diff --git a/ax25/ax25.4 b/ax25/ax25.4 new file mode 100644 index 0000000..6456971 --- /dev/null +++ b/ax25/ax25.4 @@ -0,0 +1,77 @@ +.TH AX25 4 "15 October 1996" Linux "Linux Programmer's Manual" +.SH NAME +AF_AX25 \- AX.25 amateur packet radio protocol family +.SH DESCRIPTION +.LP +.B AX.25 +is a protocol used extensively by radio amateurs. The Linux AX.25 protocol +family permits access to these protocols via the standard networking +.B socket +metaphor. +.LP +The AX.25 protocol layer supports both connected mode and datagram (UI) +frame modes. IP traffic may be stacked on top of AX.25 frames for IP +transmission over the AX.25 medium. +.LP +The primary mode of operation is connected mode which is the mode used for a +socket of type SOCK_SEQPACKET (stream sockets are not available in AX.25). +This requires that the user ensures output data is suitably packetised, and +that input data is read a packet at a time into a buffer of suitable size. +The Linux AX.25 protocol layer can operate in standard AX.25 mode with three +bit sequence numbers or in PE1CHL extended AX.25 mode which uses seven bit +sequence numbers. The protocol passed to the socket is used for all outgoing +frames. Passing 0 causes the normal AX.25 Text PID to be used. +.LP +SOCK_DGRAM gives access to AX.25 UI frames. For access to special frames (of +any form) SOCK_RAW can be used. There is no SOCK_PACKET support under AX.25. +Instead an AF_INET socket of type SOCK_PACKET should be used. +.LP +AX.25 addresses consist of 6 ascii characters and a number called the SSID. +These are encoded into a sockaddr_ax25 structure which is provided to the +relevant system calls. When digipeaters are included a callsign path can be +much more complex. When this is the case a struct full_sockaddr_ax25 should +be passed to the system calls. +.LP +AX.25 has some unusual properties. Notably in a multi-user system an AX.25 +address is often associated with a user, and some users may not have such an +association. a set of ioctl calls are provided to manage an association +table, and in addition the superuser may use an arbitary callsign by binding +to the callsign desired and specifying the port to use as a first digipeated +hop. +.LP +AX.25 supports the following socket options for SOL_AX25. AX25_T1 is the T1 +timer in 1/10ths of a second, AX25_T2 is the T2 timer in 1/10ths of a +second, AX25_T3 is the T3 timer. The window is settable with AX25_WINDOW. +AX25_N2, the retry counter is also configurable. There is no 'infinite +retry' option supported however. The method of backoff for retries is +configurable via the socket option AX25_BACKOFF, a value of true indicates +the use of exponential backoff and false simple linear backoff. The mode of +a connection made be altered to be either standard AX.25 or extended AX.25 +via AX25_EXTSEQ. It is possible to have the complete AX.25 header returned +to the application by setting AX25_HDRINCL to true, programs must be aware +of the internal structure of AX.25 frames to use this option. Note that if +AX.25 fragmentation is encountered, only the control information of the +first frame is returned along with the defragmented data. +.SH "SEE ALSO" +.BR call (1), +.BR socket (2), +.BR setsockopt (2), +.BR getsockopt (2), +.BR axctl (8), +.BR axparms (5), +.BR axassociate (8), +.BR axparms (8), +.BR kissattach (8). +.LP +.SH BUGS +.LP +Too numerous to list in full currently. +.TP 3 +\(bu +Minor protocol violations exist. +.SH AUTHOR +.nf +Alan Cox GW4PTS <alan@cymru.net> +.br +Jonathan Naylor G4KLX <g4klx@g4klx.demon.co.uk> +.fi |