net-common-support.html
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>Chapter 41. Support Features</H1
><DIV
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><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="net-common-support.html#NET-COMMON-TFTP"
>TFTP</A
></DT
><DT
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>DHCP</A
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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="NET-COMMON-TFTP"
>TFTP</A
></H1
><P
>The TFTP client and server are described in
<TT
CLASS="FILENAME"
>tftp_support.h</TT
>;</P
><P
>The TFTP client has and new and an older, deprecated, API. The
new API works for both IPv4 and IPv6 where as the deprecated API is
IPv4 only.</P
><P
>The new API is as follows:</P
><TABLE
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><TD
><PRE
CLASS="PROGRAMLISTING"
>int tftp_client_get(const char * const filename,
const char * const server,
const int port,
char *buf,
int len,
const int mode,
int * const err);
int tftp_client_put(const char * const filename,
const char * const server,
const int port,
const char *buf,
int len,
const int mode,
int *const err);</PRE
></TD
></TR
></TABLE
><P
>Currently <CODE
CLASS="VARNAME"
>server</CODE
> can only be a numeric IPv4 or
IPv6 address. The resolver is currently not used, but it is planned to
add this feature (patches welcome). If <CODE
CLASS="VARNAME"
>port</CODE
> is zero
the client connects to the default TFTP port on the server. Otherwise
the specified port is used.</P
><P
>
The deprecated API is:
<TABLE
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>int tftp_get(const char * const filename,
const struct sockaddr_in * const server,
char * buf,
int len,
const int mode,
int * const error);
int tftp_put(const char * const filename,
const struct sockaddr_in * const server,
const char * buffer,
int len,
const int mode,
int * const err);</PRE
></TD
></TR
></TABLE
></P
><P
>The <CODE
CLASS="VARNAME"
>server</CODE
> should contain the address of the
server to contact. If the <CODE
CLASS="VARNAME"
>sin_port</CODE
> member of the
structure is zero the default TFTP port is used. Otherwise the
specified port is used.</P
><P
>Both API's report errors in the same way. The functions return a value
of -1 and <CODE
CLASS="VARNAME"
>*err</CODE
> will be set to one of the
following values:</P
><TABLE
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>#define TFTP_ENOTFOUND 1 /* file not found */
#define TFTP_EACCESS 2 /* access violation */
#define TFTP_ENOSPACE 3 /* disk full or allocation exceeded */
#define TFTP_EBADOP 4 /* illegal TFTP operation */
#define TFTP_EBADID 5 /* unknown transfer ID */
#define TFTP_EEXISTS 6 /* file already exists */
#define TFTP_ENOUSER 7 /* no such user */
#define TFTP_TIMEOUT 8 /* operation timed out */
#define TFTP_NETERR 9 /* some sort of network error */
#define TFTP_INVALID 10 /* invalid parameter */
#define TFTP_PROTOCOL 11 /* protocol violation */
#define TFTP_TOOLARGE 12 /* file is larger than buffer */</PRE
></TD
></TR
></TABLE
><P
>If there are no errors the return value is the number of bytes
transfered.</P
><P
>The server is more complex. It requires a filesystem implementation
to be supplied by the user, and attached to the tftp server by means
of a vector of function pointers:</P
><TABLE
BORDER="5"
BGCOLOR="#E0E0F0"
WIDTH="70%"
><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>struct tftpd_fileops {
int (*open)(const char *, int);
int (*close)(int);
int (*write)(int, const void *, int);
int (*read)(int, void *, int);
};</PRE
></TD
></TR
></TABLE
><P
>These functions have the obvious semantics. The structure
describing the filesystem is an argument to the <CODE
CLASS="FUNCTION"
>tftpd_start</CODE
>:
<TABLE
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BGCOLOR="#E0E0F0"
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
>int tftp_start(int port,
struct tftpd_fileops *ops);</PRE
></TD
></TR
></TABLE
></P
><P
>The first argument is the port to use for the server. If this
port number is zero, the default TFTP port number will be used. The
return value from <CODE
CLASS="FUNCTION"
>tftpd_start</CODE
> is a handle which
can be passed to <CODE
CLASS="FUNCTION"
>tftpd_stop</CODE
>. This will kill the
tftpd thread. Note that this is not a clean shutdown. The thread will
simply be killed. <CODE
CLASS="FUNCTION"
>tftpd_stop</CODE
> will attempt to
close the sockets the thread was listening on and free some of its
allocated memory. But if the thread was actively transferreing data at
the time <CODE
CLASS="FUNCTION"
>tftpd_stop</CODE
> is called, it is quite likely
some memory and a socket will be leaked. Use this function with
caution (or implement a clean shutdown and please contribute the code
back :-).</P
><P
>There are two CDL configuration options that control how many
servers on how many different ports tftp can be
started. CYGSEM_NET_TFTPD_MULTITHREADED, when enabled, allows multiple
tftpd threads to operate on the same port number. With only one
thread, while the thread is active transferring data, new requests for
transfers will not be served until the active transfer is
complete. When multiple threads are started on the same port, multiple
transfers can take place simultaneous, up to the number of threads
started. However a semaphore is required to synchronise the
threads. This semaphore is required per port. The CDL option
CYGNUM_NET_TFTPD_MULTITHREADED_PORTS controls how many different port
numbers multithreaded servers can service.</P
><P
>If CYGSEM_NET_TFTPD_MULTITHREADED is not enabled, only one
thread may be run per port number. But this removes the need for a
semaphore and so CYGNUM_NET_TFTPD_MULTITHREADED_PORTS is not required
and unlimited number of ports can be used. </P
><P
>It should be noted that the TFTPD does not perform any form of
file locking. When multiple servers are active, it is assumed the
underlying filesystem will refuse to open the same file multiple
times, operate correctly with simultaneous read/writes to the same
file, or if you are unlucky, corrupt itself beyond all repair.</P
><P
>When IPv6 is enabled the tftpd thread will listen for requests
from both IPv4 and IPv6 addresses.</P
><P
>As discussed in the description of the tftp_server_test
above, an example filesystem is provided in
<TT
CLASS="FILENAME"
>net/common/<TT
CLASS="REPLACEABLE"
><I
>VERSION</I
></TT
>/src/tftp_dummy_file.c</TT
>
for
use by the tftp server test. The dummy filesystem is not a supported
part of the network stack, it exists purely for demonstration purposes.</P
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