[Python-Dev] IPv6 docs
Jun-ichiro itojun Hagino
itojun@iijlab.net
Sun, 05 Aug 2001 01:20:05 +0900
Here's a diff for adding documentation for IPv6 funcs in socket module.
I have no TeX on my laptop these days, so not sure if it compiles clean.
also if someone could go through my broken english, it would be highly
appreciated.
itojun
Index: Doc/lib/libftplib.tex
===================================================================
RCS file: /cvsroot/python/python/dist/src/Doc/lib/libftplib.tex,v
retrieving revision 1.32
diff -u -r1.32 libftplib.tex
--- Doc/lib/libftplib.tex 2001/07/06 19:28:48 1.32
+++ Doc/lib/libftplib.tex 2001/08/04 16:18:22
@@ -191,9 +191,9 @@
\begin{methoddesc}{transfercmd}{cmd\optional{, rest}}
Initiate a transfer over the data connection. If the transfer is
-active, send a \samp{PORT} command and the transfer command specified
+active, send a \samp{EPRT} or \samp{PORT} command and the transfer command specified
by \var{cmd}, and accept the connection. If the server is passive,
-send a \samp{PASV} command, connect to it, and start the transfer
+send a \samp{EPSV} or \samp{PASV} command, connect to it, and start the transfer
command. Either way, return the socket for the connection.
If optional \var{rest} is given, a \samp{REST} command is
Index: Doc/lib/libsocket.tex
===================================================================
RCS file: /cvsroot/python/python/dist/src/Doc/lib/libsocket.tex,v
retrieving revision 1.51
diff -u -r1.51 libsocket.tex
--- Doc/lib/libsocket.tex 2001/01/10 19:34:52 1.51
+++ Doc/lib/libsocket.tex 2001/08/04 16:18:24
@@ -19,6 +19,8 @@
of information on the details of socket semantics. For \UNIX, refer
to the manual pages; for Windows, see the WinSock (or Winsock 2)
specification.
+For IPv6-ready APIs, readers may want to refer to RFC2553 titled
+\cite{Basic Socket Interface Extensions for IPv6}.
The Python interface is a straightforward transliteration of the
\UNIX{} system call and library interface for sockets to Python's
@@ -30,20 +32,43 @@
receive operations is automatic, and buffer length is implicit on send
operations.
-Socket addresses are represented as a single string for the
-\constant{AF_UNIX} address family and as a pair
-\code{(\var{host}, \var{port})} for the \constant{AF_INET} address
+Socket addresses are represented as follows.
+A single string is used for the
+\constant{AF_UNIX} address family.
+A pair
+\code{(\var{host}, \var{port})} is used for the \constant{AF_INET} address
family, where \var{host} is a string representing
either a hostname in Internet domain notation like
-\code{'daring.cwi.nl'} or an IP address like \code{'100.50.200.5'},
-and \var{port} is an integral port number. Other address families are
+\code{'daring.cwi.nl'} or an IPv4 address like \code{'100.50.200.5'},
+and \var{port} is an integral port number.
+For \constant{AF_INET6} address family, a four-tuple \code{(\var{host},
+\var{port}, \var{flowinfo}, \var{scopeid})} is used, where
+\var{flowinfo} and \var{scopeid} represents \code{sin6_flowinfo}
+and \code{sin6_scope_id} member in \constant{struct sockaddr_in6}
+in C.
+For \module{socket} module methods,
+\var{flowinfo} and \var{scopeid} can be omitted just for backward compatibility.
+Note, however, omission of \var{scopeid} can cause problems in manipulating
+scoped IPv6 addresses.
+Other address families are
currently not supported. The address format required by a particular
socket object is automatically selected based on the address family
specified when the socket object was created.
-For IP addresses, two special forms are accepted instead of a host
+For IPv4 addresses, two special forms are accepted instead of a host
address: the empty string represents \constant{INADDR_ANY}, and the string
\code{'<broadcast>'} represents \constant{INADDR_BROADCAST}.
+The behavior is not available for IPv6 for backward compatibility,
+therefore, you may want to avoid these if you intend to support IPv6 with
+your Python programs.
+
+If you use a hostname in \var{host} portion of IPv4/v6 socket address,
+the program may present a nondeterministic behavior,
+as Python uses the first address returned from the DNS resolution.
+The socket address will be resolved differently into an actual
+IPv4/v6 address, depending on the results from DNS resolution and/or
+the host configuration.
+For deterministic behavior use a numeric address in \var{host} portion.
All errors raise exceptions. The normal exceptions for invalid
argument types and out-of-memory conditions can be raised; errors
@@ -57,7 +82,7 @@
\begin{excdesc}{error}
-This exception is raised for socket- or address-related errors.
+This exception is raised for socket-related errors.
The accompanying value is either a string telling what went wrong or a
pair \code{(\var{errno}, \var{string})}
representing an error returned by a system
@@ -66,8 +91,30 @@
names for the error codes defined by the underlying operating system.
\end{excdesc}
+\begin{excdesc}{herror}
+This exception is raised for address-related errors, for functions that uses
+\var{h_errno} in C API.
+It includes \function{gethostbyname} and \function{gethostbyaddr}.
+The accompanying value is either a string telling what went wrong or a
+pair \code{(\var{h_errno}, \var{string})}
+representing an error returned by a library call.
+\var{string} represents the description of \var{h_errno}, as returned
+by \cfunction{hstrerror} C API.
+\end{excdesc}
+
+\begin{excdesc}{gaierror}
+This exception is raised for address-related errors, for \function{getaddrinfo}
+and \function{getnameinfo}.
+The accompanying value is either a string telling what went wrong or a
+pair \code{(\var{error}, \var{string})}
+representing an error returned by a library call.
+\var{string} represents the description of \var{error}, as returned
+by \cfunction{gai_strerror} C API.
+\end{excdesc}
+
\begin{datadesc}{AF_UNIX}
\dataline{AF_INET}
+\dataline{AF_INET6}
These constants represent the address (and protocol) families,
used for the first argument to \function{socket()}. If the
\constant{AF_UNIX} constant is not defined then this protocol is
@@ -93,6 +140,10 @@
\dataline{IPPORT_*}
\dataline{INADDR_*}
\dataline{IP_*}
+\dataline{IPV6_*}
+\dataline{EAI_*}
+\dataline{AI_*}
+\dataline{NI_*}
Many constants of these forms, documented in the \UNIX{} documentation on
sockets and/or the IP protocol, are also defined in the socket module.
They are generally used in arguments to the \method{setsockopt()} and
@@ -101,6 +152,30 @@
for a few symbols, default values are provided.
\end{datadesc}
+\begin{funcdesc}{getaddrinfo}{host, port\optional{, family, socktype, proto, flags}}
+Resolves \var{host}/\var{port} argument,
+into a sequence of 5-tuples that contain all the necessary argument for
+the sockets manipulation.
+\var{host} is a domain name,
+an string representation of IPv4/v6 address or \code{None}.
+\var{port} is a string service name (like \code{http}),
+a numeric port number or \code{None}.
+The rest of the arguments are optional and must be numeric if specified.
+For \var{host} and \var{port}, by passing either an empty string or \code{None},
+you can pass \code{NULL} to the C API.
+The \function{getaddrinfo()} function returns a list of the following 5-tuples:
+\code{(\var{family}, \var{socktype}, \var{proto}, \var{canonname}, \var{sockaddr})}.
+\var{family}, \var{socktype}, \var{proto} are all integer and are meant to
+be passed to the \function{socket()} function.
+\var{canonname} is a string representing the canonical name of the \var{host}.
+It can be a numeric IPv4/v6 address when \code{AI_CANONNAME} is specified
+against numeric \var{host}.
+\var{sockaddr} is a tuple describing a socket address, as described above.
+See \code{Lib/httplib.py} and other library files
+for a typical usage of the function.
+\versionadded{X.0}
+\end{funcdesc}
+
\begin{funcdesc}{getfqdn}{\optional{name}}
Return a fully qualified domain name for \var{name}.
If \var{name} is omitted or empty, it is interpreted as the local
@@ -113,26 +188,33 @@
\end{funcdesc}
\begin{funcdesc}{gethostbyname}{hostname}
-Translate a host name to IP address format. The IP address is
+Translate a host name to IPv4 address format. The IPv4 address is
returned as a string, e.g., \code{'100.50.200.5'}. If the host name
-is an IP address itself it is returned unchanged. See
+is an IPv4 address itself it is returned unchanged. See
\function{gethostbyname_ex()} for a more complete interface.
+\function{gethostbyname()} does not support IPv6 name resolution, and
+\function{getaddrinfo()} should be used instead for IPv4/v6 dual stack support.
\end{funcdesc}
\begin{funcdesc}{gethostbyname_ex}{hostname}
-Translate a host name to IP address format, extended interface.
+Translate a host name to IPv4 address format, extended interface.
Return a triple \code{(hostname, aliaslist, ipaddrlist)} where
\code{hostname} is the primary host name responding to the given
\var{ip_address}, \code{aliaslist} is a (possibly empty) list of
alternative host names for the same address, and \code{ipaddrlist} is
-a list of IP addresses for the same interface on the same
+a list of IPv4 addresses for the same interface on the same
host (often but not always a single address).
+\function{gethostbyname_ex()} does not support IPv6 name resolution, and
+\function{getaddrinfo()} should be used instead for IPv4/v6 dual stack support.
\end{funcdesc}
\begin{funcdesc}{gethostname}{}
Return a string containing the hostname of the machine where
-the Python interpreter is currently executing. If you want to know the
-current machine's IP address, use \code{gethostbyname(gethostname())}.
+the Python interpreter is currently executing.
+If you want to know the current machine's IP address, you may want to use
+\code{gethostbyname(gethostname())}.
+This operation assumes that there is a valid address-to-host mapping for
+the host, and the assumption does not always hold.
Note: \function{gethostname()} doesn't always return the fully qualified
domain name; use \code{gethostbyaddr(gethostname())}
(see below).
@@ -143,10 +225,19 @@
\var{ipaddrlist})} where \var{hostname} is the primary host name
responding to the given \var{ip_address}, \var{aliaslist} is a
(possibly empty) list of alternative host names for the same address,
-and \var{ipaddrlist} is a list of IP addresses for the same interface
+and \var{ipaddrlist} is a list of IPv4/v6 addresses for the same interface
on the same host (most likely containing only a single address).
To find the fully qualified domain name, use the function
\function{getfqdn()}.
+\function{gethostbyaddr} supports both IPv4 and IPv6.
+\end{funcdesc}
+
+\begin{funcdesc}{getnameinfo}{sockaddr, flags}
+Translate a socket address \var{sockaddr} into a 2-tuple
+\code{(\var{host}, \var{port})}.
+Depending on the settings of \var{flags}, the result can contain
+a fully-qualified domain name or numeric address representation in \var{host}.
+Similarly, \var{port} can contain a string port name or a numeric port number.
\end{funcdesc}
\begin{funcdesc}{getprotobyname}{protocolname}
@@ -166,7 +257,7 @@
\begin{funcdesc}{socket}{family, type\optional{, proto}}
Create a new socket using the given address family, socket type and
-protocol number. The address family should be \constant{AF_INET} or
+protocol number. The address family should be \constant{AF_INET}, \constant{AF_INET6} or
\constant{AF_UNIX}. The socket type should be \constant{SOCK_STREAM},
\constant{SOCK_DGRAM} or perhaps one of the other \samp{SOCK_} constants.
The protocol number is usually zero and may be omitted in that case.
@@ -209,7 +300,7 @@
\end{funcdesc}
\begin{funcdesc}{inet_aton}{ip_string}
-Convert an IP address from dotted-quad string format
+Convert an IPv4 address from dotted-quad string format
(e.g.\ '123.45.67.89') to 32-bit packed binary format, as a string four
characters in length.
@@ -217,14 +308,17 @@
and needs objects of type \ctype{struct in_addr}, which is the C type
for the 32-bit packed binary this function returns.
-If the IP address string passed to this function is invalid,
+If the IPv4 address string passed to this function is invalid,
\exception{socket.error} will be raised. Note that exactly what is
valid depends on the underlying C implementation of
\cfunction{inet_aton()}.
+
+\function{inet_aton} does not support IPv6, and
+\function{getnameinfo()} should be used instead for IPv4/v6 dual stack support.
\end{funcdesc}
\begin{funcdesc}{inet_ntoa}{packed_ip}
-Convert a 32-bit packed IP address (a string four characters in
+Convert a 32-bit packed IPv4 address (a string four characters in
length) to its standard dotted-quad string representation
(e.g. '123.45.67.89').
@@ -234,6 +328,9 @@
If the string passed to this function is not exactly 4 bytes in
length, \exception{socket.error} will be raised.
+
+\function{inet_ntoa} does not support IPv6, and
+\function{getnameinfo()} should be used instead for IPv4/v6 dual stack support.
\end{funcdesc}
\begin{datadesc}{SocketType}
@@ -306,14 +403,14 @@
\begin{methoddesc}[socket]{getpeername}{}
Return the remote address to which the socket is connected. This is
-useful to find out the port number of a remote IP socket, for instance.
+useful to find out the port number of a remote IPv4/v6 socket, for instance.
(The format of the address returned depends on the address family ---
see above.) On some systems this function is not supported.
\end{methoddesc}
\begin{methoddesc}[socket]{getsockname}{}
Return the socket's own address. This is useful to find out the port
-number of an IP socket, for instance.
+number of an IPv4/v6 socket, for instance.
(The format of the address returned depends on the address family ---
see above.)
\end{methoddesc}
@@ -413,7 +510,7 @@
\subsection{Example \label{socket-example}}
-Here are two minimal example programs using the TCP/IP protocol:\ a
+Here are four minimal example programs using the TCP/IP protocol:\ a
server that echoes all data that it receives back (servicing only one
client), and a client using it. Note that a server must perform the
sequence \function{socket()}, \method{bind()}, \method{listen()},
@@ -424,6 +521,8 @@
socket it is listening on but on the new socket returned by
\method{accept()}.
+The first two examples support IPv4 only.
+
\begin{verbatim}
# Echo server program
import socket
@@ -450,6 +549,82 @@
PORT = 50007 # The same port as used by the server
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
+s.send('Hello, world')
+data = s.recv(1024)
+s.close()
+print 'Received', `data`
+\end{verbatim}
+
+The next two examples are identical to the above two, but support both
+IPv4 and IPv6.
+The server side will listen to the first address family available
+(it should listen to both instead).
+On most of IPv6-ready systems, IPv6 will take precedence
+and the server may not accept IPv4 traffic.
+The client side will try to connect to the all addresses returned as a result
+of the name resolution, and sends traffic to the first one connected
+successfully.
+
+\begin{verbatim}
+# Echo server program
+import socket
+import sys
+
+HOST = '' # Symbolic name meaning the local host
+PORT = 50007 # Arbitrary non-privileged port
+s = None
+for res in socket.getaddrinfo('', PORT, socket.AF_UNSPEC, socket.SOCK_STREAM, 0, socket.AI_PASSIVE):
+ af, socktype, proto, canonname, sa = res
+ try:
+ s = socket.socket(af, socktype, proto)
+ except socket.error, msg:
+ s = None
+ continue
+ try:
+ s.bind(sa)
+ s.listen(1)
+ except socket.error, msg:
+ s.close()
+ s = None
+ continue
+ break
+if s is None:
+ print 'could not open socket'
+ sys.exit(1)
+conn, addr = s.accept()
+print 'Connected by', addr
+while 1:
+ data = conn.recv(1024)
+ if not data: break
+ conn.send(data)
+conn.close()
+\end{verbatim}
+
+\begin{verbatim}
+# Echo client program
+import socket
+import sys
+
+HOST = 'daring.cwi.nl' # The remote host
+PORT = 50007 # The same port as used by the server
+s = None
+for res in socket.getaddrinfo(HOST, PORT, socket.AF_UNSPEC, socket.SOCK_STREAM):
+ af, socktype, proto, canonname, sa = res
+ try:
+ s = socket.socket(af, socktype, proto)
+ except socket.error, msg:
+ s = None
+ continue
+ try:
+ s.connect(sa)
+ except socket.error, msg:
+ s.close()
+ s = None
+ continue
+ break
+if s is None:
+ print 'could not open socket'
+ sys.exit(1)
s.send('Hello, world')
data = s.recv(1024)
s.close()