| // SPDX-License-Identifier: LGPL-2.1 |
| /* |
| * fs/cifs/dns_resolve.c |
| * |
| * Copyright (c) 2007 Igor Mammedov |
| * Author(s): Igor Mammedov (niallain@gmail.com) |
| * Steve French (sfrench@us.ibm.com) |
| * Wang Lei (wang840925@gmail.com) |
| * David Howells (dhowells@redhat.com) |
| * |
| * Contains the CIFS DFS upcall routines used for hostname to |
| * IP address translation. |
| * |
| */ |
| |
| #include <linux/slab.h> |
| #include <linux/dns_resolver.h> |
| #include "dns_resolve.h" |
| #include "cifsglob.h" |
| #include "cifsproto.h" |
| #include "cifs_debug.h" |
| |
| /** |
| * dns_resolve_server_name_to_ip - Resolve UNC server name to ip address. |
| * @unc: UNC path specifying the server (with '/' as delimiter) |
| * @ip_addr: Where to return the IP address. |
| * |
| * The IP address will be returned in string form, and the caller is |
| * responsible for freeing it. |
| * |
| * Returns length of result on success, -ve on error. |
| */ |
| int |
| dns_resolve_server_name_to_ip(const char *unc, char **ip_addr) |
| { |
| struct sockaddr_storage ss; |
| const char *hostname, *sep; |
| char *name; |
| int len, rc; |
| |
| if (!ip_addr || !unc) |
| return -EINVAL; |
| |
| len = strlen(unc); |
| if (len < 3) { |
| cifs_dbg(FYI, "%s: unc is too short: %s\n", __func__, unc); |
| return -EINVAL; |
| } |
| |
| /* Discount leading slashes for cifs */ |
| len -= 2; |
| hostname = unc + 2; |
| |
| /* Search for server name delimiter */ |
| sep = memchr(hostname, '/', len); |
| if (sep) |
| len = sep - hostname; |
| else |
| cifs_dbg(FYI, "%s: probably server name is whole unc: %s\n", |
| __func__, unc); |
| |
| /* Try to interpret hostname as an IPv4 or IPv6 address */ |
| rc = cifs_convert_address((struct sockaddr *)&ss, hostname, len); |
| if (rc > 0) |
| goto name_is_IP_address; |
| |
| /* Perform the upcall */ |
| rc = dns_query(current->nsproxy->net_ns, NULL, hostname, len, |
| NULL, ip_addr, NULL, false); |
| if (rc < 0) |
| cifs_dbg(FYI, "%s: unable to resolve: %*.*s\n", |
| __func__, len, len, hostname); |
| else |
| cifs_dbg(FYI, "%s: resolved: %*.*s to %s\n", |
| __func__, len, len, hostname, *ip_addr); |
| return rc; |
| |
| name_is_IP_address: |
| name = kmalloc(len + 1, GFP_KERNEL); |
| if (!name) |
| return -ENOMEM; |
| memcpy(name, hostname, len); |
| name[len] = 0; |
| cifs_dbg(FYI, "%s: unc is IP, skipping dns upcall: %s\n", |
| __func__, name); |
| *ip_addr = name; |
| return 0; |
| } |