[9fans] fs error msg: didn't like (1460 274) byte message

[9fans] fs error msg: didn't like (1460 274) byte message

[Axel Belinfante]

Just had a problem copying/saving a file from acme at home
(over a right now not excitingly fast connection)
to the fake worm server at work.
When it happened, acme hang (until I fysically disrupted the connection
-- could not think of something else) and cp also hang.
(after disrupting the connection, acme returned to a usable state,
so I could save the file to local disk -- many thanks to the person
bringing up this kind of things (hanging fs connection) some days ago!)
When it happened, I had a 'C fs' window open, in which appeared:

didn't like 1460 byte message
didn't like 274 byte message

Scenario:
working at home on a laptop that has had the 60Mb update;
the kernel is a few days older, of september 18.
Because I have this funny router at the home  end of the cable
modem connection, and it does not let il through, I have

cpu%  cat /rc/bin/service/tcp564
#!/bin/rc
exec aux/trampoline il!super!9fs
cpu%

on the cpu server and run '9fs cpu' to connect to the file server.
(the cpu server is diskless and gets root from fs; also its
kernel is from september 18, I think).

The problem seems reproducible: when saving the remote file
from acme failed, I saved it locally and tried then copying it to fs,
with the same result. However, doing a 'cat > target'
in the cpu window, and pasting the text from the (short) file there,
followed by ^D was succesful (remember, cpu server gets root from fs).

The fs kernel is a bit old, from May 28. Can that explain this?

Is there anything easy I could try to get more insight?
I tried 'flag chat' on the fs, but that did not seem
to give info on the 'not-liked' packages -- but maybe I overlooked.

I'll keep the latop running and connected, in case there are some
things I could try.

Just tried to open a new window, run 9fs cpu, and tried again to
copy the same file from local disk to remote fs. Same result.

Axel (concerned, but still hoping for a simple explanation...)

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Axel Belinfante]

I see your point about not using read9pmsg.

> this works just fine for me.
I works for me too. Thanks!

> how do you know it's 152 bytes when n == -104?
It's a(n educated?) guess.
In xfer9p I syslog-ed the message sizes (trying to read, actually read).
The 'message size traces' have the same prefix (things done 'under the hood'
for the mount command). Then it's just 'diff' by hand: these numbers
represent the first difference between a succesful trace and a failing one.

Axel.

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Russ Cox]

this works just fine for me.
does it work for you?  if not, what
are the hex bytes of the weird 152-byte
message.  how do you know it's 152 bytes
when n == -104?

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

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Russ Cox]

> I tried something like that, and what I tried did not work, but my failure
> might differ from your xfer9p (have thrown it away, cannot compare).
> Still I'm wondering, why use own code instead of simply using read9pmsg?

The reason not to use read9pmsg is that I don't want to
get caught with a buffer that's not big enough, so I realloc
it (when necessary) after reading the header length.
You can't use read9pmsg to do that unless you know
basically everything about what read9pmsg is doing, at
which point it's easier not to use it.

Or rather, it would be easier, if I could manage to write
the correct five lines.

Russ

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Axel Belinfante]

(added the same syslog debugging and)
Tried it. Works exactly like one of my previous attempts (acc. to debug log).
Works fine until it encounters a message with size=152;
then it seems that 'n = GBIT32(buf)' doesn't do what we need;
it in the next read it tries to read (n=-104)-4 bytes and fails.
Would be nice if we could use read9pmsg (all these problems solved
in one place). But then we need a solution for the varying message size.

Axel.

> The problem is the buffer can be arbitrarily sized, though
> typically 8192+IOHDRSZ is the max a client and server will
> agree on.  Cpu uses a much larger max size to improve graphics
> performance.
>
> Here's a fixed xfer9p.  I forgot that the initial count
> includes itself.

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Axel Belinfante]

> The problem is the buffer can be arbitrarily sized, though
> typically 8192+IOHDRSZ is the max a client and server will
> agree on.  Cpu uses a much larger max size to improve graphics
> performance.
>
> Here's a fixed xfer9p.  I forgot that the initial count
> includes itself.

I tried something like that, and what I tried did not work, but my failure
might differ from your xfer9p (have thrown it away, cannot compare).
Still I'm wondering, why use own code instead of simply using read9pmsg?

I'll try your xfer9p and let you know the result.

Axel.

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Russ Cox]

The problem is the buffer can be arbitrarily sized, though
typically 8192+IOHDRSZ is the max a client and server will
agree on.  Cpu uses a much larger max size to improve graphics
performance.

Here's a fixed xfer9p.  I forgot that the initial count
includes itself.

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

Russ

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Axel Belinfante]

[-- Attachment #1: Type: text/plain, Size: 625 bytes --]

Russ,
I'm not sure why your version fails (in the way I wrote before),
I assume it has something to do with reading/parsing the 9p format.
I rewrote your trampoline.c using read9pmsg. Now it seems to work.
My version follows below.
However, could you please check (improve) the buffer allocation (size)?
I just copied the constant 8192+IOHDRSZ from /sys/src/lib9p/srv.c
but I don't trust I got it correct (rephrased: is this the biggest
buffer we might need, or might we need more?). (too lazy to read the man).
I also put in some syslog debugging code that probably should
be en/disabled with a -d flag.

Axel.

[-- Attachment #2: trampoline.c --]
[-- Type: text/plain , Size: 4041 bytes --]

#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 (x == xfer9p)
		syslog(0, "trampoline", "using xfer9p");
	else
		syslog(0, "trampoline", "using xfer");

	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, m;

	nbuf = 8192+IOHDRSZ;
	buf = malloc(nbuf);
	if(buf == nil)
		sysfatal("xfer: malloc %ud: %r", nbuf);

	for(;;){
		if((n = read9pmsg(from, buf, nbuf)) <= 0){
			syslog(0, "trampoline", "read error (%d->%d): n=%d", from, to, n);
			break;
		} else
			syslog(0, "trampoline", "read ok (%d->%d): n=%d", from, to, n);
		if((m = write(to, buf, n)) != n) {
			syslog(0, "trampoline", "write error (%d->%d): (m=%d) !=(n=%d)", from, to, m, n);
			break;
		} else {
			syslog(0, "trampoline", "write ok (%d->%d): (m=%d) == (n=%d)", from, to, m, n);
		}
	}
}

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;
}

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Axel Belinfante]

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

I have tried, and mounting seems not to work.
When running 9fs or srv I get the 'post...' message,
but the actual mount does not seem to work --
9fs just hangs after the 'post...' message, and
doing a 'srv' by hand succeeds but mounting the srv hangs.

I tried both at home and at work (wavelan from laptop to cpu),
and both the cable connection at home and the wavelan at work
are pretty slow right now (ping even looses messages).

I added flags on the fs (error, il, attach) and now I get
just:
il: allocating il!130.89.145.32!...

when I run: 9fs cpu
9fs just prints post... and hangs.
When I kill it (delete), and start again: 9fs cpu
I see on the fs:

fs: didn't like 23 byte message
no protocol for message
 13 00 00 00 64 FF FF 18 20 00 00 06
hangup! closed 27179/130.89.145.32.17008

and on the laptop where I run 9fs I get:

srv cpu: mount failed: EOF receiving fversion reply

after which 9fs exits.

Axel.

Re: [9fans] fs error msg: didn't like (1460 274) byte message

[Russ Cox]

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;
}