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/*

 * DNS referrals give two main fields: the path to connect to in

 * /Netbios-host-name/share-name/path... form and a network

 * address of how to find this path of the form domain.dom.

 *

 * The domain.dom is resolved in XP/Win2k etc using AD to do

 * a lookup (this is a consensus view, I don't think anyone

 * has proved it).  I cannot do this as AD needs Kerberos and

 * LDAP which I don't have.

 *

 * Instead I just use the NetBios names passed in the paths

 * and assume that the servers are in the same DNS domain as me

 * and have their DNS hostname set the same as their netbios

 * called-name; thankfully this always seems to be the case (so far).

 *

 * I have not added support for starting another instance of

 * cifs to connect to other servers referenced in DFS links,

 * this is not a problem for me and I think it hides a load

 * of problems of its own wrt plan9's private namespaces.

 *

 * The proximity of my test server (AD enabled) is always 0 but some

 * systems may report more meaningful values.  The expiry time is

 * similarly zero, so I guess at 5 mins.

 *

 * If the redirection points to a "hidden" share (i.e., its name

 * ends in a $) then the type of the redirection is 0 (unknown) even

 * though it is a CIFS share.

 *

 * It would be nice to add a check for which subnet a server is on

 * so our first choice is always the the server on the same subnet

 * as us which replies to a ping (i.e., is up).  This could short-

 * circuit the tests as the a server on the same subnet will always

 * be the fastest to get to.

 *

 * If I set Flags2_DFS then I don't see DFS links, I just get

 * path not found (?!).

 *

 * If I do a QueryFileInfo of a DFS link point (IE when I'am doing a walk)

 * Then I just see a directory, its not until I try to walk another level

 * That I get  "IO reparse tag not handled" error rather than

 * "Path not covered".

 *

 * If I check the extended attributes of the QueryFileInfo in walk() then I can

 * see this is a reparse point and so I can get the referral.  The only

 * problem here is that samba and the like may not support this.

 */

#include <u.h>

#include <libc.h>

#include <fcall.h>

#include <thread.h>

#include <libsec.h>

#include <ctype.h>

#include <9p.h>

#include "cifs.h"

enum {

	Nomatch,	/* not found in cache */

	Exactmatch,	/* perfect match found */

	Badmatch	/* matched but wrong case */

};

#define SINT_MAX	0x7fffffff

typedef struct Dfscache Dfscache;

struct Dfscache {

	Dfscache*next;		/* next entry */

	char	*src;

	char	*host;

	char	*share;

	char	*path;

	long	expiry;		/* expiry time in sec */

	long	rtt;		/* round trip time, nsec */

	int	prox;		/* proximity, lower = closer */

};

Dfscache *Cache;

int

dfscacheinfo(Fmt *f)

{

	long ex;

	Dfscache *cp;

	for(cp = Cache; cp; cp = cp->next){

		ex = cp->expiry - time(nil);

		if(ex < 0)

			ex = -1;

		fmtprint(f, "%-42s %6ld %8.1f %4d %-16s %-24s %s\n",

			cp->src, ex, (double)cp->rtt/1000.0L, cp->prox,

			cp->host, cp->share, cp->path);

	}

	return 0;

}

char *

trimshare(char *s)

{

	char *p;

	static char name[128];

	strncpy(name, s, sizeof(name));

	name[sizeof(name)-1] = 0;

	if((p = strrchr(name, '$')) != nil && p[1] == 0)

		*p = 0;

	return name;

}

static Dfscache *

lookup(char *path, int *match)

{

	int len, n, m;

	Dfscache *cp, *best;

	if(match)

		*match = Nomatch;

	len = 0;

	best = nil;

	m = strlen(path);

	for(cp = Cache; cp; cp = cp->next){

		n = strlen(cp->src);

		if(n < len)

			continue;

		if(strncmp(path, cp->src, n) != 0)

			continue;

		if(path[n] != 0 && path[n] != '/')

			continue;

		best = cp;

		len = n;

		if(n == m){

			if(match)

				*match = Exactmatch;

			break;

		}

	}

	return best;

}

char *

mapfile(char *opath)

{

	int exact;

	Dfscache *cp;

	char *p, *path;

	static char npath[MAX_DFS_PATH];

	path = opath;

	if((cp = lookup(path, &exact)) != nil){

		snprint(npath, sizeof npath, "/%s%s%s%s", cp->share,

			*cp->path? "/": "", cp->path, path + strlen(cp->src));

		path = npath;

	}

	if((p = strchr(path+1, '/')) == nil)

		p = "/";

	if(Debug && strstr(Debug, "dfs") != nil)

		print("mapfile src=%q => dst=%q\n", opath, p);

	return p;

}

int

mapshare(char *path, Share **osp)

{

	int i;

	Share *sp;

	Dfscache *cp;

	char *s, *try;

	char *tail[] = { "", "$" };

	if((cp = lookup(path, nil)) == nil)

		return 0;

	for(sp = Shares; sp < Shares+Nshares; sp++){

		s = trimshare(sp->name);

		if(cistrcmp(cp->share, s) != 0)

			continue;

		if(Checkcase && strcmp(cp->share, s) != 0)

			continue;

		if(Debug && strstr(Debug, "dfs") != nil)

			print("mapshare, already connected, src=%q => dst=%q\n", path, sp->name);

		*osp = sp;

		return 0;

	}

	/*

	 * Try to autoconnect to share if it is not known.  Note even if you

	 * didn't specify any shares and let the system autoconnect you may

	 * not already have the share you need as RAP (which we use) throws

	 * away names > 12 chars long.  If we where to use RPC then this block

	 * of code would be less important, though it would still be useful

	 * to catch Shares added since cifs(1) was started.

	 */

	sp = Shares + Nshares;

	for(i = 0; i < 2; i++){

		try = smprint("%s%s", cp->share, tail[i]);

		if(CIFStreeconnect(Sess, Sess->cname, try, sp) == 0){

			sp->name = try;

			*osp = sp;

			Nshares++;

			if(Debug && strstr(Debug, "dfs") != nil)

				print("mapshare connected, src=%q dst=%q\n",

					path, cp->share);

			return 0;

		}

		free(try);

	}

	if(Debug && strstr(Debug, "dfs") != nil)

		print("mapshare failed src=%s\n", path);

	werrstr("not found");

	return -1;

}

/*

 * Rtt_tol is the fractional tollerance for RTT comparisons.

 * If a later (further down the list) host's RTT is less than

 * 1/Rtt_tol better than my current best then I don't bother

 * with it.  This biases me towards entries at the top of the list

 * which Active Directory has already chosen for me and prevents

 * noise in RTTs from pushing me to more distant machines.

 */

static int

remap(Dfscache *cp, Refer *re)

{

	int n;

	long rtt;

	char *p, *a[4];

	enum {

		Hostname = 1,

		Sharename = 2,

		Pathname = 3,

		Rtt_tol = 10

	};

	if(Debug && strstr(Debug, "dfs") != nil)

		print("	remap %s\n", re->addr);

	for(p = re->addr; *p; p++)

		if(*p == '\\')

			*p = '/';

	if(cp->prox < re->prox){

		if(Debug && strstr(Debug, "dfs") != nil)

			print("	remap %d < %d\n", cp->prox, re->prox);

		return -1;

	}

	if((n = getfields(re->addr, a, sizeof(a), 0, "/")) < 3){

		if(Debug && strstr(Debug, "dfs") != nil)

			print("	remap nfields=%d\n", n);

		return -1;

	}

	if((rtt = ping(a[Hostname], Dfstout)) == -1){

		if(Debug && strstr(Debug, "dfs") != nil)

			print("	remap ping failed\n");

		return -1;

	}

	if(cp->rtt < rtt && (rtt/labs(rtt-cp->rtt)) < Rtt_tol){

		if(Debug && strstr(Debug, "dfs") != nil)

			print("	remap bad ping %ld < %ld && %ld < %d\n",

				cp->rtt, rtt, (rtt/labs(rtt-cp->rtt)), Rtt_tol);

		return -1;

	}

	if(n < 4)

		a[Pathname] = "";

	if(re->ttl == 0)

		re->ttl = 60*5;

	free(cp->host);

	free(cp->share);

	free(cp->path);

	cp->rtt = rtt;

	cp->prox = re->prox;

	cp->expiry = time(nil)+re->ttl;

	cp->host = estrdup9p(a[Hostname]);

	cp->share = estrdup9p(trimshare(a[Sharename]));

	cp->path = estrdup9p(a[Pathname]);

	if(Debug && strstr(Debug, "dfs") != nil)

		print("	remap ping OK prox=%d host=%s share=%s path=%s\n",

			cp->prox, cp->host, cp->share, cp->path);

	return 0;

}

static int

redir1(Session *s, char *path, Dfscache *cp, int level)

{

	Refer retab[16], *re;

	int n, gflags, used, found;

	if(level > 8)

		return -1;

	if((n = T2getdfsreferral(s, &Ipc, path, &gflags, &used, retab,

	    nelem(retab))) == -1)

		return -1;

	if(! (gflags & DFS_HEADER_ROOT))

		used = SINT_MAX;

	found = 0;

	for(re = retab; re < retab+n; re++){

		if(Debug && strstr(Debug, "dfs") != nil)

			print("referal level=%d prox=%d path=%q addr=%q\n",

				level, re->prox, re->path, re->addr);

		if(gflags & DFS_HEADER_STORAGE){

			if(remap(cp, re) == 0)

				found = 1;

		} else{

			if(redir1(s, re->addr, cp, level+1) != -1)  /* ???? */

				found = 1;

		}

		free(re->addr);

		free(re->path);

	}

	if(Debug && strstr(Debug, "dfs") != nil)

		print("referal level=%d path=%q found=%d used=%d\n",

			level, path, found, used);

	if(!found)

		return -1;

	return used;

}

/*

 * We can afford to ignore the used count returned by redir

 * because of the semantics of 9p - we always walk to directories

 * ome and we a time and we always walk before any other file operations

 */

int

redirect(Session *s, Share *sp, char *path)

{

	int match;

	char *unc;

	Dfscache *cp;

	if(Debug && strstr(Debug, "dfs") != nil)

		print("redirect name=%q path=%q\n", sp->name, path);

	cp = lookup(path, &match);

	if(match == Badmatch)

		return -1;

	if(cp && match == Exactmatch){

		if(cp->expiry >= time(nil)){		/* cache hit */

			if(Debug && strstr(Debug, "dfs") != nil)

				print("redirect cache=hit src=%q => share=%q path=%q\n",

					cp->src, cp->share, cp->path);

			return 0;

		} else{				/* cache hit, but entry stale */

			cp->rtt = SINT_MAX;

			cp->prox = SINT_MAX;

			unc = smprint("//%s/%s/%s%s%s", s->auth->windom,

				cp->share, cp->path, *cp->path? "/": "",

				path + strlen(cp->src) + 1);

			if(unc == nil)

				sysfatal("no memory: %r");

			if(redir1(s, unc, cp, 1) == -1){

				if(Debug && strstr(Debug, "dfs") != nil)

					print("redirect refresh failed unc=%q\n",

						unc);

				free(unc);

				return -1;

			}

			free(unc);

			if(Debug && strstr(Debug, "dfs") != nil)

				print("redirect refresh cache=stale src=%q => share=%q path=%q\n",

					cp->src, cp->share, cp->path);

			return 0;

		}

	}

	/* in-exact match or complete miss */

	if(cp)

		unc = smprint("//%s/%s/%s%s%s", s->auth->windom, cp->share,

			cp->path, *cp->path? "/": "", path + strlen(cp->src) + 1);

	else

		unc = smprint("//%s%s", s->auth->windom, path);

	if(unc == nil)

		sysfatal("no memory: %r");

	cp = emalloc9p(sizeof(Dfscache));

	memset(cp, 0, sizeof(Dfscache));

	cp->rtt = SINT_MAX;

	cp->prox = SINT_MAX;

	if(redir1(s, unc, cp, 1) == -1){

		if(Debug && strstr(Debug, "dfs") != nil)

			print("redirect new failed unc=%q\n", unc);

		free(unc);

		free(cp);

		return -1;

	}

	free(unc);

	cp->src = estrdup9p(path);

	cp->next = Cache;

	Cache = cp;

	if(Debug && strstr(Debug, "dfs") != nil)

		print("redirect cache=miss src=%q => share=%q path=%q\n",

			cp->src, cp->share, cp->path);

	return 0;

}