path: root/utils/mountd/cache.c

/*
 * Handle communication with knfsd internal cache
 *
 * We open /proc/net/rpc/{auth.unix.ip,nfsd.export,nfsd.fh}/channel
 * and listen for requests (using my_svc_run)
 * 
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <sys/types.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/vfs.h>
#include <time.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <ctype.h>
#include <pwd.h>
#include <grp.h>
#include <mntent.h>
#include "misc.h"
#include "nfslib.h"
#include "exportfs.h"
#include "mountd.h"
#include "xmalloc.h"
#include "fsloc.h"
#include "pseudoflavors.h"

#ifdef USE_BLKID
#include "blkid/blkid.h"
#endif

/*
 * Invoked by RPC service loop
 */
void	cache_set_fds(fd_set *fdset);
int	cache_process_req(fd_set *readfds);

enum nfsd_fsid {
	FSID_DEV = 0,
	FSID_NUM,
	FSID_MAJOR_MINOR,
	FSID_ENCODE_DEV,
	FSID_UUID4_INUM,
	FSID_UUID8,
	FSID_UUID16,
	FSID_UUID16_INUM,
};

/*
 * Support routines for text-based upcalls.
 * Fields are separated by spaces.
 * Fields are either mangled to quote space tab newline slosh with slosh
 * or a hexified with a leading \x
 * Record is terminated with newline.
 *
 */
static int cache_export_ent(char *domain, struct exportent *exp, char *p);


char *lbuf  = NULL;
int lbuflen = 0;
extern int use_ipaddr;

static void auth_unix_ip(FILE *f)
{
	/* requests are
	 *  class IP-ADDR
	 * Ignore if class != "nfsd"
	 * Otherwise find domainname and write back:
	 *
	 *  "nfsd" IP-ADDR expiry domainname
	 */
	char *cp;
	char class[20];
	char ipaddr[INET6_ADDRSTRLEN];
	char *client = NULL;
	struct addrinfo *tmp = NULL;
	struct addrinfo *ai = NULL;
	if (readline(fileno(f), &lbuf, &lbuflen) != 1)
		return;

	xlog(D_CALL, "auth_unix_ip: inbuf '%s'", lbuf);

	cp = lbuf;

	if (qword_get(&cp, class, 20) <= 0 ||
	    strcmp(class, "nfsd") != 0)
		return;

	if (qword_get(&cp, ipaddr, sizeof(ipaddr)) <= 0)
		return;

	tmp = host_pton(ipaddr);
	if (tmp == NULL)
		return;

	auth_reload();

	/* addr is a valid, interesting address, find the domain name... */
	if (!use_ipaddr) {
		ai = client_resolve(tmp->ai_addr);
		client = client_compose(ai);
		freeaddrinfo(ai);
	}
	freeaddrinfo(tmp);

	qword_print(f, "nfsd");
	qword_print(f, ipaddr);
	qword_printint(f, time(0)+30*60);
	if (use_ipaddr)
		qword_print(f, ipaddr);
	else if (client)
		qword_print(f, *client?client:"DEFAULT");
	qword_eol(f);
	xlog(D_CALL, "auth_unix_ip: client %p '%s'", client, client?client: "DEFAULT");

	free(client);
}

static void auth_unix_gid(FILE *f)
{
	/* Request are
	 *  uid
	 * reply is
	 *  uid expiry count list of group ids
	 */
	uid_t uid;
	struct passwd *pw;
	gid_t glist[100], *groups = glist;
	int ngroups = 100;
	int rv, i;
	char *cp;

	if (readline(fileno(f), &lbuf, &lbuflen) != 1)
		return;

	cp = lbuf;
	if (qword_get_uint(&cp, &uid) != 0)
		return;

	pw = getpwuid(uid);
	if (!pw)
		rv = -1;
	else {
		rv = getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups);
		if (rv == -1 && ngroups >= 100) {
			groups = malloc(sizeof(gid_t)*ngroups);
			if (!groups)
				rv = -1;
			else
				rv = getgrouplist(pw->pw_name, pw->pw_gid,
						  groups, &ngroups);
		}
	}
	qword_printuint(f, uid);
	qword_printuint(f, time(0)+30*60);
	if (rv >= 0) {
		qword_printuint(f, ngroups);
		for (i=0; i<ngroups; i++)
			qword_printuint(f, groups[i]);
	} else
		qword_printuint(f, 0);
	qword_eol(f);

	if (groups != glist)
		free(groups);
}

#if USE_BLKID
static const char *get_uuid_blkdev(char *path)
{
	/* We set *safe if we know that we need the
	 * fsid from statfs too.
	 */
	static blkid_cache cache = NULL;
	struct stat stb;
	char *devname;
	blkid_tag_iterate iter;
	blkid_dev dev;
	const char *type;
	const char *val, *uuid = NULL;

	if (cache == NULL)
		blkid_get_cache(&cache, NULL);

	if (stat(path, &stb) != 0)
		return NULL;
	devname = blkid_devno_to_devname(stb.st_dev);
	if (!devname)
		return NULL;
	dev = blkid_get_dev(cache, devname, BLKID_DEV_NORMAL);
	free(devname);
	if (!dev)
		return NULL;
	iter = blkid_tag_iterate_begin(dev);
	if (!iter)
		return NULL;
	while (blkid_tag_next(iter, &type, &val) == 0) {
		if (strcmp(type, "UUID") == 0)
			uuid = val;
		if (strcmp(type, "TYPE") == 0 &&
		    strcmp(val, "btrfs") == 0) {
			uuid = NULL;
			break;
		}
	}
	blkid_tag_iterate_end(iter);
	return uuid;
}
#else
#define get_uuid_blkdev(path) (NULL)
#endif

static int get_uuid(const char *val, int uuidlen, char *u)
{
	/* extract hex digits from uuidstr and compose a uuid
	 * of the given length (max 16), xoring bytes to make
	 * a smaller uuid.
	 */
	int i = 0;
	
	memset(u, 0, uuidlen);
	for ( ; *val ; val++) {
		char c = *val;
		if (!isxdigit(c))
			continue;
		if (isalpha(c)) {
			if (isupper(c))
				c = c - 'A' + 10;
			else
				c = c - 'a' + 10;
		} else
			c = c - '0' + 0;
		if ((i&1) == 0)
			c <<= 4;
		u[i/2] ^= c;
		i++;
		if (i == uuidlen*2)
			i = 0;
	}
	return 1;
}

static int uuid_by_path(char *path, int type, int uuidlen, char *uuid)
{
	/* get a uuid for the filesystem found at 'path'.
	 * There are several possible ways of generating the
	 * uuids (types).
	 * Type 0 is used for new filehandles, while other types
	 * may be used to interpret old filehandle - to ensure smooth
	 * forward migration.
	 * We return 1 if a uuid was found (and it might be worth 
	 * trying the next type) or 0 if no more uuid types can be
	 * extracted.
	 */

	/* Possible sources of uuid are
	 * - blkid uuid
	 * - statfs64 uuid
	 *
	 * On some filesystems (e.g. vfat) the statfs64 uuid is simply an
	 * encoding of the device that the filesystem is mounted from, so
	 * it we be very bad to use that (as device numbers change).  blkid
	 * must be preferred.
	 * On other filesystems (e.g. btrfs) the statfs64 uuid contains
	 * important info that the blkid uuid cannot contain:  This happens
	 * when multiple subvolumes are exported (they have the same
	 * blkid uuid but different statfs64 uuids).
	 * We rely on get_uuid_blkdev *knowing* which is which and not returning
	 * a uuid for filesystems where the statfs64 uuid is better.
	 *
	 */
	struct statfs64 st;
	char fsid_val[17];
	const char *blkid_val;
	const char *val;

	blkid_val = get_uuid_blkdev(path);

	if (statfs64(path, &st) == 0 &&
	    (st.f_fsid.__val[0] || st.f_fsid.__val[1]))
		snprintf(fsid_val, 17, "%08x%08x",
			 st.f_fsid.__val[0], st.f_fsid.__val[1]);
	else
		fsid_val[0] = 0;

	if (blkid_val && (type--) == 0)
		val = blkid_val;
	else if (fsid_val[0] && (type--) == 0)
		val = fsid_val;
	else
		return 0;

	get_uuid(val, uuidlen, uuid);
	return 1;
}

/* Iterate through /etc/mtab, finding mountpoints
 * at or below a given path
 */
static char *next_mnt(void **v, char *p)
{
	FILE *f;
	struct mntent *me;
	int l = strlen(p);
	if (*v == NULL) {
		f = setmntent("/etc/mtab", "r");
		*v = f;
	} else
		f = *v;
	while ((me = getmntent(f)) != NULL &&
	       (strncmp(me->mnt_dir, p, l) != 0 ||
		me->mnt_dir[l] != '/'))
		;
	if (me == NULL) {
		endmntent(f);
		*v = NULL;
		return NULL;
	}
	return me->mnt_dir;
}

static void nfsd_fh(FILE *f)
{
	/* request are:
	 *  domain fsidtype fsid
	 * interpret fsid, find export point and options, and write:
	 *  domain fsidtype fsid expiry path
	 */
	char *cp;
	char *dom;
	int fsidtype;
	int fsidlen;
	unsigned int dev, major=0, minor=0;
	unsigned int inode=0;
	unsigned long long inode64;
	unsigned int fsidnum=0;
	char fsid[32];
	struct exportent *found = NULL;
	struct addrinfo *ai = NULL;
	char *found_path = NULL;
	nfs_export *exp;
	int i;
	int dev_missing = 0;
	int uuidlen = 0;
	char *fhuuid = NULL;

	if (readline(fileno(f), &lbuf, &lbuflen) != 1)
		return;

	xlog(D_CALL, "nfsd_fh: inbuf '%s'", lbuf);

	cp = lbuf;
	
	dom = malloc(strlen(cp));
	if (dom == NULL)
		return;
	if (qword_get(&cp, dom, strlen(cp)) <= 0)
		goto out;
	if (qword_get_int(&cp, &fsidtype) != 0)
		goto out;
	if (fsidtype < 0 || fsidtype > 7)
		goto out; /* unknown type */
	if ((fsidlen = qword_get(&cp, fsid, 32)) <= 0)
		goto out;
	switch(fsidtype) {
	case FSID_DEV: /* 4 bytes: 2 major, 2 minor, 4 inode */
		if (fsidlen != 8)
			goto out;
		memcpy(&dev, fsid, 4);
		memcpy(&inode, fsid+4, 4);
		major = ntohl(dev)>>16;
		minor = ntohl(dev) & 0xFFFF;
		break;

	case FSID_NUM: /* 4 bytes - fsid */
		if (fsidlen != 4)
			goto out;
		memcpy(&fsidnum, fsid, 4);
		break;

	case FSID_MAJOR_MINOR: /* 12 bytes: 4 major, 4 minor, 4 inode 
		 * This format is never actually used but was
		 * an historical accident
		 */
		if (fsidlen != 12)
			goto out;
		memcpy(&dev, fsid, 4); major = ntohl(dev);
		memcpy(&dev, fsid+4, 4); minor = ntohl(dev);
		memcpy(&inode, fsid+8, 4);
		break;

	case FSID_ENCODE_DEV: /* 8 bytes: 4 byte packed device number, 4 inode */
		/* This is *host* endian, not net-byte-order, because
		 * no-one outside this host has any business interpreting it
		 */
		if (fsidlen != 8)
			goto out;
		memcpy(&dev, fsid, 4);
		memcpy(&inode, fsid+4, 4);
		major = (dev & 0xfff00) >> 8;
		minor = (dev & 0xff) | ((dev >> 12) & 0xfff00);
		break;

	case FSID_UUID4_INUM: /* 4 byte inode number and 4 byte uuid */
		if (fsidlen != 8)
			goto out;
		memcpy(&inode, fsid, 4);
		uuidlen = 4;
		fhuuid = fsid+4;
		break;
	case FSID_UUID8: /* 8 byte uuid */
		if (fsidlen != 8)
			goto out;
		uuidlen = 8;
		fhuuid = fsid;
		break;
	case FSID_UUID16: /* 16 byte uuid */
		if (fsidlen != 16)
			goto out;
		uuidlen = 16;
		fhuuid = fsid;
		break;
	case FSID_UUID16_INUM: /* 8 byte inode number and 16 byte uuid */
		if (fsidlen != 24)
			goto out;
		memcpy(&inode64, fsid, 8);
		inode = inode64;
		uuidlen = 16;
		fhuuid = fsid+8;
		break;
	}

	auth_reload();

	/* Now determine export point for this fsid/domain */
	for (i=0 ; i < MCL_MAXTYPES; i++) {
		nfs_export *next_exp;
		for (exp = exportlist[i].p_head; exp; exp = next_exp) {
			struct stat stb;
			char u[16];
			char *path;
			int type;

			if (exp->m_export.e_flags & NFSEXP_CROSSMOUNT) {
				static nfs_export *prev = NULL;
				static void *mnt = NULL;
				
				if (prev == exp) {
					/* try a submount */
					path = next_mnt(&mnt, exp->m_export.e_path);
					if (!path) {
						next_exp = exp->m_next;
						prev = NULL;
						continue;
					}
					next_exp = exp;
				} else {
					prev = exp;
					mnt = NULL;
					path = exp->m_export.e_path;
					next_exp = exp;
				}
			} else {
				path = exp->m_export.e_path;
				next_exp = exp->m_next;
			}

			if (!use_ipaddr && !client_member(dom, exp->m_client->m_hostname))
				continue;
			if (exp->m_export.e_mountpoint &&
			    !is_mountpoint(exp->m_export.e_mountpoint[0]?
					   exp->m_export.e_mountpoint:
					   exp->m_export.e_path))
				dev_missing ++;
			if (stat(path, &stb) != 0)
				continue;
			if (!S_ISDIR(stb.st_mode) && !S_ISREG(stb.st_mode)) {
				continue;
			}
			switch(fsidtype){
			case FSID_DEV:
			case FSID_MAJOR_MINOR:
			case FSID_ENCODE_DEV:
				if (stb.st_ino != inode)
					continue;
				if (major != major(stb.st_dev) ||
				    minor != minor(stb.st_dev))
					continue;
				break;
			case FSID_NUM:
				if (((exp->m_export.e_flags & NFSEXP_FSID) == 0 ||
				     exp->m_export.e_fsid != fsidnum))
					continue;
				break;
			case FSID_UUID4_INUM:
			case FSID_UUID16_INUM:
				if (stb.st_ino != inode)
					continue;
				goto check_uuid;
			case FSID_UUID8:
			case FSID_UUID16:
				if (!is_mountpoint(path))
					continue;
			check_uuid:
				if (exp->m_export.e_uuid)
					get_uuid(exp->m_export.e_uuid,
						 uuidlen, u);
				else
					for (type = 0;
					     uuid_by_path(path, type, uuidlen, u);
					     type++)
						if (memcmp(u, fhuuid, uuidlen) == 0)
							break;

				if (memcmp(u, fhuuid, uuidlen) != 0)
					continue;
				break;
			}
			if (use_ipaddr) {
				if (ai == NULL) {
					struct addrinfo *tmp;
					tmp = host_pton(dom);
					if (tmp == NULL)
						goto out;
					ai = client_resolve(tmp->ai_addr);
					freeaddrinfo(tmp);
				}
				if (!client_check(exp->m_client, ai))
					continue;
			}
			/* It's a match !! */
			if (!found) {
				found = &exp->m_export;
				found_path = strdup(path);
				if (found_path == NULL)
					goto out;
			} else if (strcmp(found->e_path, exp->m_export.e_path)!= 0)
			{
				xlog(L_WARNING, "%s and %s have same filehandle for %s, using first",
				     found_path, path, dom);
			}
		}
	}
	if (found && 
	    found->e_mountpoint &&
	    !is_mountpoint(found->e_mountpoint[0]?
			   found->e_mountpoint:
			   found->e_path)) {
		/* Cannot export this yet 
		 * should log a warning, but need to rate limit
		   xlog(L_WARNING, "%s not exported as %d not a mountpoint",
		   found->e_path, found->e_mountpoint);
		 */
		/* FIXME we need to make sure we re-visit this later */
		goto out;
	}
	if (!found && dev_missing) {
		/* The missing dev could be what we want, so just be
		 * quite rather than returning stale yet
		 */
		goto out;
	}

	if (found)
		if (cache_export_ent(dom, found, found_path) < 0)
			found = 0;

	qword_print(f, dom);
	qword_printint(f, fsidtype);
	qword_printhex(f, fsid, fsidlen);
	/* The fsid -> path lookup can be quite expensive as it
	 * potentially stats and reads lots of devices, and some of those
	 * might have spun-down.  The Answer is not likely to
	 * change underneath us, and an 'exportfs -f' can always
	 * remove this from the kernel, so use a really log
	 * timeout.  Maybe this should be configurable on the command
	 * line.
	 */
	qword_printint(f, 0x7fffffff);
	if (found)
		qword_print(f, found_path);
	qword_eol(f);
 out:
	if (found_path)
		free(found_path);
	freeaddrinfo(ai);
	free(dom);
	xlog(D_CALL, "nfsd_fh: found %p path %s", found, found ? found->e_path : NULL);
	return;		
}

static void write_fsloc(FILE *f, struct exportent *ep)
{
	struct servers *servers;

	if (ep->e_fslocmethod == FSLOC_NONE)
		return;

	servers = replicas_lookup(ep->e_fslocmethod, ep->e_fslocdata);
	if (!servers)
		return;
	qword_print(f, "fsloc");
	qword_printint(f, servers->h_num);
	if (servers->h_num >= 0) {
		int i;
		for (i=0; i<servers->h_num; i++) {
			qword_print(f, servers->h_mp[i]->h_host);
			qword_print(f, servers->h_mp[i]->h_path);
		}
	}
	qword_printint(f, servers->h_referral);
	release_replicas(servers);
}

static void write_secinfo(FILE *f, struct exportent *ep, int flag_mask)
{
	struct sec_entry *p;

	for (p = ep->e_secinfo; p->flav; p++)
		; /* Do nothing */
	if (p == ep->e_secinfo) {
		/* There was no sec= option */
		return;
	}
	qword_print(f, "secinfo");
	qword_printint(f, p - ep->e_secinfo);
	for (p = ep->e_secinfo; p->flav; p++) {
		qword_printint(f, p->flav->fnum);
		qword_printint(f, p->flags & flag_mask);
	}

}

static int dump_to_cache(FILE *f, char *domain, char *path, struct exportent *exp)
{
	qword_print(f, domain);
	qword_print(f, path);
	qword_printint(f, time(0)+30*60);
	if (exp) {
		int different_fs = strcmp(path, exp->e_path) != 0;
		int flag_mask = different_fs ? ~NFSEXP_FSID : ~0;

		qword_printint(f, exp->e_flags & flag_mask);
		qword_printint(f, exp->e_anonuid);
		qword_printint(f, exp->e_anongid);
		qword_printint(f, exp->e_fsid);
		write_fsloc(f, exp);
		write_secinfo(f, exp, flag_mask);
 		if (exp->e_uuid == NULL || different_fs) {
 			char u[16];
 			if (uuid_by_path(path, 0, 16, u)) {
 				qword_print(f, "uuid");
 				qword_printhex(f, u, 16);
 			}
 		} else {
 			char u[16];
 			get_uuid(exp->e_uuid, 16, u);
 			qword_print(f, "uuid");
 			qword_printhex(f, u, 16);
 		}
	}
	return qword_eol(f);
}

static int is_subdirectory(char *child, char *parent)
{
	int l = strlen(parent);

	return strcmp(child, parent) == 0
		|| (strncmp(child, parent, l) == 0 && child[l] == '/');
}

static int path_matches(nfs_export *exp, char *path)
{
	if (exp->m_export.e_flags & NFSEXP_CROSSMOUNT)
		return is_subdirectory(path, exp->m_export.e_path);
	return strcmp(path, exp->m_export.e_path) == 0;
}

static int
client_matches(nfs_export *exp, char *dom, struct addrinfo *ai)
{
	if (use_ipaddr)
		return client_check(exp->m_client, ai);
	return client_member(dom, exp->m_client->m_hostname);
}

static int
export_matches(nfs_export *exp, char *dom, char *path, struct addrinfo *ai)
{
	return path_matches(exp, path) && client_matches(exp, dom, ai);
}

static nfs_export *
lookup_export(char *dom, char *path, struct addrinfo *ai)
{
	nfs_export *exp;
	nfs_export *found = NULL;
	int found_type = 0;
	int i;

	for (i=0 ; i < MCL_MAXTYPES; i++) {
		for (exp = exportlist[i].p_head; exp; exp = exp->m_next) {
			if (!export_matches(exp, dom, path, ai))
				continue;
			if (!found) {
				found = exp;
				found_type = i;
				continue;
			}

			/* Always prefer non-V4ROOT mounts */
			if (found->m_export.e_flags & NFSEXP_V4ROOT)
				continue;

			/* If one is a CROSSMOUNT, then prefer the longest path */
			if (((found->m_export.e_flags & NFSEXP_CROSSMOUNT) ||
			     (exp->m_export.e_flags & NFSEXP_CROSSMOUNT)) &&
			    strlen(found->m_export.e_path) !=
			    strlen(exp->m_export.e_path)) {

				if (strlen(exp->m_export.e_path) >
				    strlen(found->m_export.e_path)) {
					found = exp;
					found_type = i;
				}
				continue;

			} else if (found_type == i && found->m_warned == 0) {
				xlog(L_WARNING, "%s exported to both %s and %s, "
				     "arbitrarily choosing options from first",
				     path, found->m_client->m_hostname, exp->m_client->m_hostname,
				     dom);
				found->m_warned = 1;
			}
		}
	}
	return found;
}

static void nfsd_export(FILE *f)
{
	/* requests are:
	 *  domain path
	 * determine export options and return:
	 *  domain path expiry flags anonuid anongid fsid
	 */

	char *cp;
	char *dom, *path;
	nfs_export *found = NULL;
	struct addrinfo *ai = NULL;

	if (readline(fileno(f), &lbuf, &lbuflen) != 1)
		return;

	xlog(D_CALL, "nfsd_export: inbuf '%s'", lbuf);

	cp = lbuf;
	dom = malloc(strlen(cp));
	path = malloc(strlen(cp));

	if (!dom || !path)
		goto out;

	if (qword_get(&cp, dom, strlen(lbuf)) <= 0)
		goto out;
	if (qword_get(&cp, path, strlen(lbuf)) <= 0)
		goto out;

	auth_reload();

	if (use_ipaddr) {
		struct addrinfo *tmp;
		tmp = host_pton(dom);
		if (tmp == NULL)
			goto out;
		ai = client_resolve(tmp->ai_addr);
		freeaddrinfo(tmp);
			goto out;
	}

	found = lookup_export(dom, path, ai);

	if (found) {
		if (dump_to_cache(f, dom, path, &found->m_export) < 0) {
			xlog(L_WARNING,
			     "Cannot export %s, possibly unsupported filesystem"
			     " or fsid= required", path);
			dump_to_cache(f, dom, path, NULL);
		}
	} else {
		dump_to_cache(f, dom, path, NULL);
	}
 out:
	xlog(D_CALL, "nfsd_export: found %p path %s", found, path ? path : NULL);
	if (dom) free(dom);
	if (path) free(path);
	freeaddrinfo(ai);
}


struct {
	char *cache_name;
	void (*cache_handle)(FILE *f);
	FILE *f;
} cachelist[] = {
	{ "auth.unix.ip", auth_unix_ip, NULL},
	{ "auth.unix.gid", auth_unix_gid, NULL},
	{ "nfsd.export", nfsd_export, NULL},
	{ "nfsd.fh", nfsd_fh, NULL},
	{ NULL, NULL, NULL }
};

extern int manage_gids;

/**
 * cache_open - prepare communications channels with kernel RPC caches
 *
 */
void cache_open(void) 
{
	int i;
	for (i=0; cachelist[i].cache_name; i++ ) {
		char path[100];
		if (!manage_gids && cachelist[i].cache_handle == auth_unix_gid)
			continue;
		sprintf(path, "/proc/net/rpc/%s/channel", cachelist[i].cache_name);
		cachelist[i].f = fopen(path, "r+");
	}
}

/**
 * cache_set_fds - prepare cache file descriptors for one iteration of the service loop
 * @fdset: pointer to fd_set to prepare
 */
void cache_set_fds(fd_set *fdset)
{
	int i;
	for (i=0; cachelist[i].cache_name; i++) {
		if (cachelist[i].f)
			FD_SET(fileno(cachelist[i].f), fdset);
	}
}

/**
 * cache_process_req - process any active cache file descriptors during service loop iteration
 * @fdset: pointer to fd_set to examine for activity
 */
int cache_process_req(fd_set *readfds) 
{
	int i;
	int cnt = 0;
	for (i=0; cachelist[i].cache_name; i++) {
		if (cachelist[i].f != NULL &&
		    FD_ISSET(fileno(cachelist[i].f), readfds)) {
			cnt++;
			cachelist[i].cache_handle(cachelist[i].f);
			FD_CLR(fileno(cachelist[i].f), readfds);
		}
	}
	return cnt;
}


/*
 * Give IP->domain and domain+path->options to kernel
 * % echo nfsd $IP  $[now+30*60] $domain > /proc/net/rpc/auth.unix.ip/channel
 * % echo $domain $path $[now+30*60] $options $anonuid $anongid $fsid > /proc/net/rpc/nfsd.export/channel
 */

static int cache_export_ent(char *domain, struct exportent *exp, char *path)
{
	int err;
	FILE *f = fopen("/proc/net/rpc/nfsd.export/channel", "w");
	if (!f)
		return -1;

	err = dump_to_cache(f, domain, exp->e_path, exp);
	if (err) {
		xlog(L_WARNING,
		     "Cannot export %s, possibly unsupported filesystem or"
		     " fsid= required", exp->e_path);
	}

	while (err == 0 && (exp->e_flags & NFSEXP_CROSSMOUNT) && path) {
		/* really an 'if', but we can break out of
		 * a 'while' more easily */
		/* Look along 'path' for other filesystems
		 * and export them with the same options
		 */
		struct stat stb;
		size_t l = strlen(exp->e_path);
		__dev_t dev;

		if (strlen(path) <= l || path[l] != '/' ||
		    strncmp(exp->e_path, path, l) != 0)
			break;
		if (stat(exp->e_path, &stb) != 0)
			break;
		dev = stb.st_dev;
		while(path[l] == '/') {
			char c;
			/* errors for submount should fail whole filesystem */
			int err2;

			l++;
			while (path[l] != '/' && path[l])
				l++;
			c = path[l];
			path[l] = 0;
			err2 = lstat(path, &stb);
			path[l] = c;
			if (err2 < 0)
				break;
			if (stb.st_dev == dev)
				continue;
			dev = stb.st_dev;
			path[l] = 0;
			dump_to_cache(f, domain, path, exp);
			path[l] = c;
		}
		break;
	}

	fclose(f);
	return err;
}

/**
 * cache_export - Inform kernel of a new nfs_export
 * @exp: target nfs_export
 * @path: NUL-terminated C string containing export path
 */
int cache_export(nfs_export *exp, char *path)
{
	char buf[INET6_ADDRSTRLEN];
	int err;
	FILE *f;

	f = fopen("/proc/net/rpc/auth.unix.ip/channel", "w");
	if (!f)
		return -1;


	qword_print(f, "nfsd");
	qword_print(f,
		host_ntop(get_addrlist(exp->m_client, 0), buf, sizeof(buf)));
	qword_printint(f, time(0)+30*60);
	qword_print(f, exp->m_client->m_hostname);
	err = qword_eol(f);
	
	fclose(f);

	err = cache_export_ent(exp->m_client->m_hostname, &exp->m_export, path)
		|| err;
	return err;
}

/**
 * cache_get_filehandle - given an nfs_export, get its root filehandle
 * @exp: target nfs_export
 * @len: length of requested file handle
 * @p: NUL-terminated C string containing export path
 *
 * Returns pointer to NFS file handle of root directory of export
 *
 * { 
 *   echo $domain $path $length 
 *   read filehandle <&0
 * } <> /proc/fs/nfsd/filehandle
 */
struct nfs_fh_len *
cache_get_filehandle(nfs_export *exp, int len, char *p)
{
	FILE *f = fopen("/proc/fs/nfsd/filehandle", "r+");
	char buf[200];
	char *bp = buf;
	int failed;
	static struct nfs_fh_len fh;

	if (!f)
		f = fopen("/proc/fs/nfs/filehandle", "r+");
	if (!f)
		return NULL;

	qword_print(f, exp->m_client->m_hostname);
	qword_print(f, p);
	qword_printint(f, len);	
	failed = qword_eol(f);
	
	if (!failed)
		failed = (fgets(buf, sizeof(buf), f) == NULL);
	fclose(f);
	if (failed)
		return NULL;
	memset(fh.fh_handle, 0, sizeof(fh.fh_handle));
	fh.fh_size = qword_get(&bp, (char *)fh.fh_handle, NFS3_FHSIZE);
	return &fh;
}