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Diffstat (limited to 'utils/statd/callback.c')
| -rw-r--r-- | utils/statd/callback.c | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/utils/statd/callback.c b/utils/statd/callback.c new file mode 100644 index 0000000..bb7c590 --- /dev/null +++ b/utils/statd/callback.c @@ -0,0 +1,122 @@ +/* + * 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 <unistd.h> +#include <netdb.h> + +#include "rpcmisc.h" +#include "statd.h" +#include "notlist.h" +#include "ha-callout.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); + + if (!statd_present_address(sap, ip_addr, sizeof(ip_addr))) { + xlog_warn("Unrecognized sender address"); + return ((void *) &result); + } + + ha_callout("sm-notify", argp->mon_name, ip_addr, 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); + } + + /* 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); +} |