From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <b725e9c5d41e55c4280f3e5db5bb3bd3@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] fs error msg: didn't like (1460 274) byte message
From: "Russ Cox" <rsc@plan9.bell-labs.com>
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Date: Tue, 24 Sep 2002 19:42:24 -0400
Topicbox-Message-UUID: f479c51c-eaca-11e9-9e20-41e7f4b1d025

Oops.  I wonder why we never noticed that before.
The problem is that TCP lost the race, and a 1734 byte
message got turned into a 1460 and a 2764.  Since IL
preserves message delimiters, the file server choked
on the two halves.  Here's a new aux/trampoline.  Run
aux/trampoline -9 and it should do the right thing
as far as putting the 9P messages back together before
passing them along.

Let me know if it works, and I'll put it on sources.
Russ


#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ndb.h>
#include <fcall.h>

enum
{
	Maxpath=	128,
};

typedef struct Endpoints Endpoints;
struct Endpoints
{
	char 	*net;
	char	*lsys;
	char	*lserv;
	char	*rsys;
	char	*rserv;
};

void		xfer(int, int);
void		xfer9p(int, int);
Endpoints*	getendpoints(char*);
void		freeendpoints(Endpoints*);
char*		iptomac(char*, char*);
int		macok(char*);

void
main(int argc, char **argv)
{
	int fd;
	int checkmac = 0;
	Endpoints *ep;
	char *mac;
	void (*x)(int, int);

	x = xfer;
	ARGBEGIN{
	case 'm':
		checkmac = 1;
		break;
	case '9':
		x = xfer9p;
		break;
	}ARGEND;

	if(argc < 1){
		fprint(2, "usage: %s dialstring\n", argv0);
		exits("usage");
	}
	if(checkmac && argc > 1){
		ep = getendpoints(argv[1]);
		mac = iptomac(ep->rsys, ep->net);
		if(!macok(mac)){
			syslog(0, "trampoline", "badmac %s from %s!%s for %s!%s on %s",
				mac, ep->rsys, ep->rserv, ep->lsys, ep->lserv, ep->net);
			exits("bad mac");
		}
	}
	fd = dial(argv[0], 0, 0, 0);
	if(fd < 0){
		fprint(2, "%s: dialing %s: %r\n", argv0, argv[0]);
		exits("dial");
	}
	rfork(RFNOTEG);
	switch(fork()){
	case -1:
		fprint(2, "%s: fork: %r\n", argv0);
		exits("dial");
	case 0:
		(*x)(0, fd);
		break;
	default:
		(*x)(fd, 1);
		break;
	}
	postnote(PNGROUP, getpid(), "die yankee pig dog");
	exits(0);
}

void
xfer(int from, int to)
{
	char buf[12*1024];
	int n;

	while((n = read(from, buf, sizeof buf)) > 0)
		if(write(to, buf, n) < 0)
			break;
}

void
xfer9p(int from, int to)
{
	char *buf;
	uint nbuf;
	int n;

	nbuf = 256;
	buf = malloc(nbuf);
	if(buf == nil)
		sysfatal("xfer: malloc %ud: %r", nbuf);

	for(;;){
		if(readn(from, buf, 4) != 4)
			break;
		n = GBIT32(buf);
		if(4+n > nbuf){
			nbuf = 4+n+8192;
			buf = realloc(buf, nbuf);
			if(buf == nil)
				sysfatal("xfer: realloc %ud: %r", nbuf);
		}
		if(readn(from, buf+4, n) != n)
			break;
		if(write(to, buf, 4+n) != 4+n)
			break;
	}
}

void
getendpoint(char *dir, char *file, char **sysp, char **servp)
{
	int fd, n;
	char buf[Maxpath];
	char *sys, *serv;

	sys = serv = 0;

	snprint(buf, sizeof buf, "%s/%s", dir, file);
	fd = open(buf, OREAD);
	if(fd >= 0){
		n = read(fd, buf, sizeof(buf)-1);
		if(n>0){
			buf[n-1] = 0;
			serv = strchr(buf, '!');
			if(serv){
				*serv++ = 0;
				serv = strdup(serv);
			}
			sys = strdup(buf);
		}
		close(fd);
	}
	if(serv == 0)
		serv = strdup("unknown");
	if(sys == 0)
		sys = strdup("unknown");
	*servp = serv;
	*sysp = sys;
}

Endpoints *
getendpoints(char *dir)
{
	Endpoints *ep;
	char *p;

	ep = malloc(sizeof(*ep));
	ep->net = strdup(dir);
	p = strchr(ep->net+1, '/');
	if(p == nil){
		free(ep->net);
		ep->net = "/net";
	} else
		*p = 0;
	getendpoint(dir, "local", &ep->lsys, &ep->lserv);
	getendpoint(dir, "remote", &ep->rsys, &ep->rserv);
	return ep;
}

void
freeendpoints(Endpoints *ep)
{
	free(ep->lsys);
	free(ep->rsys);
	free(ep->lserv);
	free(ep->rserv);
	free(ep);
}

char*
iptomac(char *ip, char *net)
{
	char file[Maxpath];
	Biobuf *b;
	char *p;
	char *f[5];

	snprint(file, sizeof(file), "%s/arp", net);
	b = Bopen(file, OREAD);
	if(b == nil)
		return nil;
	while((p = Brdline(b, '\n')) != nil){
		p[Blinelen(b)-1] = 0;
		if(tokenize(p, f, nelem(f)) < 4)
			continue;
		if(strcmp(f[1], "OK") == 0
		&& strcmp(f[2], ip) == 0){
			p = strdup(f[3]);
			Bterm(b);
			return p;
		}
	}
	Bterm(b);
	return nil;
}

int
macok(char *mac)
{
	Ndbtuple *tp;
	char buf[Ndbvlen];

	if(mac == nil)
		return 0;
	tp = csgetval("/net", "ether", mac, "trampok", buf);
	if(tp == nil)
		return 0;
	ndbfree(tp);
	return 1;
}