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