mirror of https://github.com/torvalds/linux.git
107 lines
2.8 KiB
C
107 lines
2.8 KiB
C
// SPDX-License-Identifier: LGPL-2.1
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/*
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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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*/
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#include <linux/inet.h>
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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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static int resolve_name(const char *name, size_t namelen,
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struct sockaddr *addr, time64_t *expiry)
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{
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char *ip;
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int rc;
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rc = dns_query(current->nsproxy->net_ns, NULL, name,
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namelen, NULL, &ip, expiry, 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__, (int)namelen, (int)namelen, name);
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} else {
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cifs_dbg(FYI, "%s: resolved: %*.*s to %s expiry %llu\n",
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__func__, (int)namelen, (int)namelen, name, ip,
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expiry ? (*expiry) : 0);
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rc = cifs_convert_address(addr, ip, strlen(ip));
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kfree(ip);
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if (!rc) {
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cifs_dbg(FYI, "%s: unable to determine ip address\n",
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__func__);
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rc = -EHOSTUNREACH;
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} else {
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rc = 0;
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}
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}
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return rc;
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}
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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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* @dom: optional DNS domain name
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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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* @expiry: Where to return the expiry time for the dns record.
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*
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* Returns zero success, -ve on error.
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*/
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int dns_resolve_server_name_to_ip(const char *dom, const char *unc,
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struct sockaddr *ip_addr, time64_t *expiry)
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{
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const char *name;
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size_t namelen, len;
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char *s;
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int rc;
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if (!ip_addr || !unc)
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return -EINVAL;
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cifs_dbg(FYI, "%s: dom=%s unc=%s\n", __func__, dom, unc);
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if (strlen(unc) < 3)
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return -EINVAL;
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extract_unc_hostname(unc, &name, &namelen);
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if (!namelen)
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return -EINVAL;
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cifs_dbg(FYI, "%s: hostname=%.*s\n", __func__, (int)namelen, name);
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/* Try to interpret hostname as an IPv4 or IPv6 address */
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rc = cifs_convert_address(ip_addr, name, namelen);
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if (rc > 0) {
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cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %*.*s\n",
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__func__, (int)namelen, (int)namelen, name);
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return 0;
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}
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/*
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* If @name contains a NetBIOS name and @dom has been specified, then
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* convert @name to an FQDN and try resolving it first.
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*/
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if (dom && *dom && cifs_netbios_name(name, namelen)) {
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len = strnlen(dom, CIFS_MAX_DOMAINNAME_LEN) + namelen + 2;
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s = kmalloc(len, GFP_KERNEL);
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if (!s)
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return -ENOMEM;
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scnprintf(s, len, "%.*s.%s", (int)namelen, name, dom);
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rc = resolve_name(s, len - 1, ip_addr, expiry);
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kfree(s);
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if (!rc)
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return 0;
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}
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return resolve_name(name, namelen, ip_addr, expiry);
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}
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