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/*
* Copyright (C) 1995, 1997-1999 Jeffrey A. Uphoff
* Modified by Olaf Kirch, Oct. 1996.
* Modified by Lon Hohberger, Oct. 2000.
*
* NSM for Linux.
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <netdb.h>
#include "rpcmisc.h"
#include "statd.h"
#include "notlist.h"
/* Callback notify list. */
/* notify_list *cbnl = NULL; ... never used */
/*
* Services SM_NOTIFY requests.
*
* When NLM uses an SM_MON request to tell statd to monitor a remote,
* the request contains a "mon_name" argument. This is usually the
* "caller_name" argument of an NLMPROC_LOCK request. On Linux, the
* NLM can send statd the remote's IP address instead of its
* caller_name. The NSM protocol does not allow both the remote's
* caller_name and it's IP address to be sent in the same SM_MON
* request.
*
* The remote's caller_name is useful because it makes it simple
* to identify rebooting remotes by matching the "mon_name" argument
* they sent via an SM_NOTIFY request.
*
* The caller_name string may not be a fully qualified domain name,
* or even registered in the DNS database, however. Having the
* remote's IP address is useful because then there is no ambiguity
* about where to send an SM_NOTIFY after the local system reboots.
*
* Without the actual caller_name, however, statd must use an
* heuristic to match an incoming SM_NOTIFY request to one of the
* hosts it is currently monitoring. The incoming mon_name in an
* SM_NOTIFY address is converted to a list of IP addresses using
* DNS. Each mon_name on statd's monitor list is also converted to
* an address list, and the two lists are checked to see if there is
* a matching address.
*
* There are some risks to this strategy:
*
* 1. The external DNS database is not reliable. It can change
* over time, or the forward and reverse mappings could be
* inconsistent.
*
* 2. If statd's monitor list becomes substantial, finding a match
* can generate a not inconsequential amount of DNS traffic.
*
* 3. statd is a single-threaded service. When DNS becomes slow or
* unresponsive, statd also becomes slow or unresponsive.
*
* 4. If the remote does not have a DNS entry at all (or if the
* remote can resolve itself, but the local host can't resolve
* the remote's hostname), the remote cannot be monitored, and
* therefore NLM locking cannot be provided for that host.
*
* 5. Local DNS resolution can produce different results for the
* mon_name than the results the remote might see for the same
* query, especially if the remote did not send a caller_name
* or mon_name that is a fully qualified domain name.
*
* Note that a caller_name is passed from NFS client to server,
* but the client never knows what mon_name the server might use
* to notify it of a reboot. On Linux, the client extracts the
* server's name from the devname it was passed by the mount
* command. This is often not a fully-qualified domain name.
*/
void *
sm_notify_1_svc(struct stat_chge *argp, struct svc_req *rqstp)
{
notify_list *lp, *call;
static char *result = NULL;
struct sockaddr *sap = nfs_getrpccaller(rqstp->rq_xprt);
char ip_addr[INET6_ADDRSTRLEN];
xlog(D_CALL, "Received SM_NOTIFY from %s, state: %d",
argp->mon_name, argp->state);
/* quick check - don't bother if we're not monitoring anyone */
if (rtnl == NULL) {
xlog_warn("SM_NOTIFY from %s while not monitoring any hosts",
argp->mon_name);
return ((void *) &result);
}
if (!statd_present_address(sap, ip_addr, sizeof(ip_addr))) {
xlog_warn("Unrecognized sender address");
return ((void *) &result);
}
/* okir change: statd doesn't remove the remote host from its
* internal monitor list when receiving an SM_NOTIFY call from
* it. Lockd will want to continue monitoring the remote host
* until it issues an SM_UNMON call.
*/
for (lp = rtnl ; lp ; lp = lp->next)
if (NL_STATE(lp) != argp->state &&
(statd_matchhostname(argp->mon_name, lp->dns_name) ||
statd_matchhostname(ip_addr, lp->dns_name))) {
NL_STATE(lp) = argp->state;
call = nlist_clone(lp);
nlist_insert(¬ify, call);
}
return ((void *) &result);
}
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