mirror of
https://mirrors.bfsu.edu.cn/git/linux.git
synced 2024-12-01 08:04:22 +08:00
506c1da44f
We recently fixed DNS resolution of the server hostname during reconnect. However, server IP address may change, even when the old one continues to server (although sub-optimally). We should schedule the next DNS resolution based on the TTL of the DNS record used for the last resolution. This way, we resolve the server hostname again when a DNS record expires. Signed-off-by: Shyam Prasad N <sprasad@microsoft.com> Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz> Cc: <stable@vger.kernel.org> # v5.11+ Signed-off-by: Steve French <stfrench@microsoft.com>
91 lines
2.3 KiB
C
91 lines
2.3 KiB
C
// 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.
|
|
* @expiry: Where to return the expiry time for the dns record.
|
|
*
|
|
* 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, time64_t *expiry)
|
|
{
|
|
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, expiry, 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 expiry %llu\n",
|
|
__func__, len, len, hostname, *ip_addr,
|
|
expiry ? (*expiry) : 0);
|
|
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;
|
|
}
|