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d0660f0b3b
Allow used DNS resolver keys to be invalidated after use if the caller is
doing its own caching of the results. This reduces the amount of resources
required.
Fix AFS to invalidate DNS results to kill off permanent failure records
that get lodged in the resolver keyring and prevent future lookups from
happening.
Fixes: 0a5143f2f8 ("afs: Implement VL server rotation")
Signed-off-by: David Howells <dhowells@redhat.com>
100 lines
2.9 KiB
C
100 lines
2.9 KiB
C
/*
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* fs/cifs/dns_resolve.c
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*
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* Copyright (c) 2007 Igor Mammedov
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* Author(s): Igor Mammedov (niallain@gmail.com)
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* Steve French (sfrench@us.ibm.com)
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* Wang Lei (wang840925@gmail.com)
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* David Howells (dhowells@redhat.com)
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*
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* Contains the CIFS DFS upcall routines used for hostname to
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* IP address translation.
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*
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* This library is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as published
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* by the Free Software Foundation; either version 2.1 of the License, or
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* (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See
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* the GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this library; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/slab.h>
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#include <linux/dns_resolver.h>
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#include "dns_resolve.h"
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#include "cifsglob.h"
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#include "cifsproto.h"
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#include "cifs_debug.h"
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/**
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* dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
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* @unc: UNC path specifying the server (with '/' as delimiter)
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* @ip_addr: Where to return the IP address.
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*
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* The IP address will be returned in string form, and the caller is
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* responsible for freeing it.
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*
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* Returns length of result on success, -ve on error.
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*/
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int
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dns_resolve_server_name_to_ip(const char *unc, char **ip_addr)
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{
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struct sockaddr_storage ss;
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const char *hostname, *sep;
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char *name;
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int len, rc;
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if (!ip_addr || !unc)
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return -EINVAL;
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len = strlen(unc);
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if (len < 3) {
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cifs_dbg(FYI, "%s: unc is too short: %s\n", __func__, unc);
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return -EINVAL;
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}
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/* Discount leading slashes for cifs */
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len -= 2;
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hostname = unc + 2;
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/* Search for server name delimiter */
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sep = memchr(hostname, '/', len);
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if (sep)
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len = sep - hostname;
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else
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cifs_dbg(FYI, "%s: probably server name is whole unc: %s\n",
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__func__, unc);
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/* Try to interpret hostname as an IPv4 or IPv6 address */
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rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len);
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if (rc > 0)
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goto name_is_IP_address;
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/* Perform the upcall */
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rc = dns_query(NULL, hostname, len, NULL, ip_addr, NULL, false);
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if (rc < 0)
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cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n",
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__func__, len, len, hostname);
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else
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cifs_dbg(FYI, "%s: resolved: %*.*s to %s\n",
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__func__, len, len, hostname, *ip_addr);
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return rc;
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name_is_IP_address:
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name = kmalloc(len + 1, GFP_KERNEL);
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if (!name)
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return -ENOMEM;
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memcpy(name, hostname, len);
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name[len] = 0;
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cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %s\n",
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__func__, name);
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*ip_addr = name;
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return 0;
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}
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