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[bug-inetutils] plan9 like socket interface
From: |
Alfred M. Szmidt |
Subject: |
[bug-inetutils] plan9 like socket interface |
Date: |
Tue, 29 Nov 2011 11:40:23 -0500 |
I've been quite annoyed over how one does sockets on unixoid system
for sometimes, specially with all the idiosyncrasies of IPv4 vs. IPv6.
Plan 9 has a quite nice API that is very much agnostic when it comes
to IPv6, IPv4, ICMP, UDP, TCP, ... etc. Now, I haven't used it at
all, and maybe it is not flexible enough for our purpose. Here is
what a basic ping might look like,
void
ping (char **s)
{
...
fd = dial (netmkaddr (s, "icmp", "1"), 0, 0, 0);
if (fd < 0) exit (1);
... create an ICMP header in buf
if (write (fd, buf, len) < len) exit (1);
n = read (fd, buf, sizeof buf);
if (n <= 0) exit (1);
...
}
Do you think that this is a good idea?
===File ~/inetutils/dial.txt================================
DIAL(3) DIAL(3)
NAME
dial, announce, listen, accept, reject, netmkaddr,
getnetconninfo, freenetconninfo, dialparse - make and break
network connections
SYNOPSIS
#include <u.h>
#include <libc.h>
int dial(char *addr, char *local, char *dir, int *cfdp)
int announce(char *addr, char *dir)
int listen(char *dir, char *newdir)
int accept(int ctl, char *dir)
int reject(int ctl, char *dir, char *cause)
char* netmkaddr(char *addr, char *defnet, char *defservice)
NetConnInfo* getnetconninfo(char *dir, int fd)
void freenetconninfo(NetConnINfo*)
int dialparse(char *addr, char **net, char **unix,
u32int *host, int *port)
DESCRIPTION
For these routines, addr is a network address of the form
network!netaddr!service, network!netaddr, or simply netaddr.
Network is tcp, udp, unix, or the special token, net. Net is
a free variable that stands for any network in common between
the source and the host netaddr. Netaddr can be a host name,
a domain name, or a network address.
On Plan 9, the dir argument is a path name to a line directory
that has files for accessing the connection. To keep the same
function signatures, the Unix port of these routines uses
strings of the form /dev/fd/n instead of line directory paths.
These strings should be treated as opaque data and ignored.
Dial makes a call to destination addr on a multiplexed
network. If the network in addr is net, dial will try in
succession all networks in common between source and
destination until a call succeeds. It returns a file
descriptor open for reading and writing the call. If the
network allows the local address to be set, as is the case
with UDP and TCP port numbers, and local is non-zero, the
local address will be set to local. Dial.s dir and cfdp
arguments are not supported and must be zero.
Announce and listen are the complements of dial. Announce
establishes a network name to which calls can be made. Like
dial, announce returns an open ctl file. The netaddr used in
announce may be a local address or an asterisk, to indicate
all local addresses, e.g. tcp!*!echo. The listen routine
takes as its first argument the dir of a previous announce.
When a call is received, listen returns an open ctl file for
the line the call was received on. It sets newdir to the path
name of the new line directory. Accept accepts a call
received by listen, while reject refuses the call because of
cause. Accept returns a file descriptor for the data file
opened ORDWR.
Netmkaddr makes an address suitable for dialing or announcing.
It takes an address along with a default network and service
to use if they are not specified in the address. It returns a
pointer to static data holding the actual address to use.
Netmkaddr also translates Unix conventions into Plan 9 syntax.
If addr is the name of a local file or Unix domain socket,
netmkaddr will return unix!addr. If addr is of the form
host:port, netmkaddr will return net!host!port.
Dialparse parses a network address as described above into a
network name, a Unix domain socket address, an IPv4 host
address, and an IPv4 port number.
Getnetconninfo returns a structure containing information
about a network connection. The structure is:
typedef struct NetConnInfo NetConnInfo;
struct NetConnInfo
{
char *dir; /* connection directory */
char *root; /* network root */
char *spec; /* binding spec */
char *lsys; /* local system */
char *lserv; /* local service */
char *rsys; /* remote system */
char *rserv; /* remote service */
char *laddr; /* local address */
char *raddr; /* remote address */
};
The information is obtained from the .line directory. dir, or
if dir is nil, from the connection file descriptor fd.
Getnetconninfo returns either a completely specified
structure, or nil if either the structure can.t be allocated
or the network directory can.t be determined. The structure
is freed using freenetconninfo.
EXAMPLES
Make a call and return an open file descriptor to use for
communications:
int
callkremvax(void)
{
return dial("kremvax", 0, 0, 0);
}
Connect to a Unix socket served by acme(4):
int
dialacme(void)
{
return dial("unix!/tmp/ns.ken.:0/acme", 0, 0, 0);
}
Announce as kremvax on TCP/IP and loop forever receiving calls
and echoing back to the caller anything sent:
int
bekremvax(void)
{
int dfd, acfd, lcfd;
char adir[40], ldir[40];
int n;
char buf[256];
acfd = announce("tcp!*!7", adir);
if(acfd < 0)
return .1;
for(;;){
/* listen for a call */
lcfd = listen(adir, ldir);
if(lcfd < 0)
return .1;
/* fork a process to echo */
switch(fork()){
case .1:
perror("forking");
close(lcfd);
break;
case 0:
/* accept the call and open the data file */
dfd = accept(lcfd, ldir);
if(dfd < 0)
return .1;
/* echo until EOF */
while((n = read(dfd, buf, sizeof(buf))) > 0)
write(dfd, buf, n);
exits(0);
default:
close(lcfd);
break;
}
}
}
SOURCE
/usr/local/plan9/src/lib9/dial.c
/usr/local/plan9/src/lib9/announce.c
/usr/local/plan9/src/lib9/_p9dialparse.c
/usr/local/plan9/src/lib9/getnetconn.c
DIAGNOSTICS
Dial, announce, and listen return .1 if they fail.
BUGS
To avoid name conflicts with the underlying system, dial,
announce, listen, netmkaddr, and reject are preprocessor
macros defined as p9dial, p9announce, and so on; see intro(3).
============================================================
- [bug-inetutils] plan9 like socket interface,
Alfred M. Szmidt <=