cachepc-linux

Fork of AMDESE/linux with modifications for CachePC side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-linux
Log | Files | Refs | README | LICENSE | sfeed.txt

dns_resolve.c (2338B)

      1// SPDX-License-Identifier: LGPL-2.1
      2/*
      3 *
      4 *   Copyright (c) 2007 Igor Mammedov
      5 *   Author(s): Igor Mammedov (niallain@gmail.com)
      6 *              Steve French (sfrench@us.ibm.com)
      7 *              Wang Lei (wang840925@gmail.com)
      8 *		David Howells (dhowells@redhat.com)
      9 *
     10 *   Contains the CIFS DFS upcall routines used for hostname to
     11 *   IP address translation.
     12 *
     13 */
     14
     15#include <linux/slab.h>
     16#include <linux/dns_resolver.h>
     17#include "dns_resolve.h"
     18#include "cifsglob.h"
     19#include "cifsproto.h"
     20#include "cifs_debug.h"
     21
     22/**
     23 * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address.
     24 * @unc: UNC path specifying the server (with '/' as delimiter)
     25 * @ip_addr: Where to return the IP address.
     26 * @expiry: Where to return the expiry time for the dns record.
     27 *
     28 * The IP address will be returned in string form, and the caller is
     29 * responsible for freeing it.
     30 *
     31 * Returns length of result on success, -ve on error.
     32 */
     33int
     34dns_resolve_server_name_to_ip(const char *unc, char **ip_addr, time64_t *expiry)
     35{
     36	struct sockaddr_storage ss;
     37	const char *hostname, *sep;
     38	char *name;
     39	int len, rc;
     40
     41	if (!ip_addr || !unc)
     42		return -EINVAL;
     43
     44	len = strlen(unc);
     45	if (len < 3) {
     46		cifs_dbg(FYI, "%s: unc is too short: %s\n", __func__, unc);
     47		return -EINVAL;
     48	}
     49
     50	/* Discount leading slashes for cifs */
     51	len -= 2;
     52	hostname = unc + 2;
     53
     54	/* Search for server name delimiter */
     55	sep = memchr(hostname, '/', len);
     56	if (sep)
     57		len = sep - hostname;
     58	else
     59		cifs_dbg(FYI, "%s: probably server name is whole unc: %s\n",
     60			 __func__, unc);
     61
     62	/* Try to interpret hostname as an IPv4 or IPv6 address */
     63	rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len);
     64	if (rc > 0)
     65		goto name_is_IP_address;
     66
     67	/* Perform the upcall */
     68	rc = dns_query(current->nsproxy->net_ns, NULL, hostname, len,
     69		       NULL, ip_addr, expiry, false);
     70	if (rc < 0)
     71		cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n",
     72			 __func__, len, len, hostname);
     73	else
     74		cifs_dbg(FYI, "%s: resolved: %*.*s to %s expiry %llu\n",
     75			 __func__, len, len, hostname, *ip_addr,
     76			 expiry ? (*expiry) : 0);
     77	return rc;
     78
     79name_is_IP_address:
     80	name = kmalloc(len + 1, GFP_KERNEL);
     81	if (!name)
     82		return -ENOMEM;
     83	memcpy(name, hostname, len);
     84	name[len] = 0;
     85	cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %s\n",
     86		 __func__, name);
     87	*ip_addr = name;
     88	return 0;
     89}