89 lines
2.2 KiB
C
89 lines
2.2 KiB
C
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// 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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/**
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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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* @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
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dns_resolve_server_name_to_ip(const char *unc, struct sockaddr *ip_addr, time64_t *expiry)
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{
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const char *hostname, *sep;
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char *ip;
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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(ip_addr, hostname, len);
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if (rc > 0) {
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cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %*.*s\n", __func__, len, len,
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hostname);
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return 0;
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}
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/* Perform the upcall */
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rc = dns_query(current->nsproxy->net_ns, NULL, hostname, len,
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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__, len, len, hostname);
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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__, len, len, hostname, ip,
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expiry ? (*expiry) : 0);
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rc = cifs_convert_address(ip_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", __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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return rc;
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}
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