ref: 87de3d34335e20fdb2ad2c471f89173aa6610193
dir: /sys/src/cmd/cifs/dfs.c/
/*
* 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 expiry of my test server (AD enabled) is always 0 but some
* systems may report more meaningful values.
*
* If the redirection points to a "hidden" share (i.e., its name
* ends in a $) then the type of the redirection is 0 (unknown) even
* though it is a CIFS share.
*
* It would be nice to add a check for which subnet a server is on
* so our first choice is always the the server on the same subnet
* as us which replies to a ping (i.e., is up). This could short-
* circuit the tests as the a server on the same subnet will always
* be the fastest to get to.
*
* If I set Flags2_DFS then I don't see DFS links, I just get
* path not found (?!).
*
* If I do a QueryFileInfo of a DFS link point (IE when I'am doing a walk)
* Then I just see a directory, its not until I try to walk another level
* That I get "IO reparse tag not handled" error rather than
* "Path not covered".
*
* If I check the extended attributes of the QueryFileInfo in walk() then I can
* see this is a reparse point and so I can get the referral. The only
* problem here is that samba and the like may not support this.
*/
#include <u.h>
#include <libc.h>
#include <fcall.h>
#include <thread.h>
#include <libsec.h>
#include <ctype.h>
#include <9p.h>
#include "cifs.h"
enum {
Nomatch, /* not found in cache */
Exactmatch, /* perfect match found */
Badmatch /* matched but wrong case */
};
#define SINT_MAX 0x7fffffff
typedef struct Dfscache Dfscache;
struct Dfscache {
Dfscache*next; /* next entry */
char *src;
char *host;
char *share;
char *path;
long expiry; /* expiry time in sec */
long rtt; /* round trip time, nsec */
};
Dfscache *Cache;
int
dfscacheinfo(Fmt *f)
{
long ex;
Dfscache *cp;
for(cp = Cache; cp; cp = cp->next){
ex = cp->expiry - time(nil);
if(ex < 0)
ex = -1;
fmtprint(f, "%-42s %6ld %8.1f %-16s %-24s %s\n",
cp->src, ex, (double)cp->rtt/1000.0L,
cp->host, cp->share, cp->path);
}
return 0;
}
char *
trimshare(char *s)
{
char *p;
static char name[128];
strncpy(name, s, sizeof(name));
name[sizeof(name)-1] = 0;
if((p = strrchr(name, '$')) != 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((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->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 host=%s share=%s path=%s\n",
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 > 16)
return -1;
if((n = T2getdfsreferral(s, &Ipc, path, &gflags, &used, retab,
nelem(retab))) == -1)
return -1;
if(! (gflags & DFS_HEADER_ROOT))
used = 9999;
found = 0;
for(re = retab; re < retab+n; re++){
if(Debug && strstr(Debug, "dfs") != nil)
print("referal level=%d path=%q addr=%q\n",
level, re->path, re->addr);
if(*re->path == 0 || *re->addr == 0){
free(re->addr);
free(re->path);
continue;
}
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;
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));
cp->rtt = 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;
}