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// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS cell alias detection
*
* Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
*/
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <keys/rxrpc-type.h>
#include "internal.h"
/*
* Sample a volume.
*/
static struct afs_volume *afs_sample_volume(struct afs_cell *cell, struct key *key,
const char *name, unsigned int namelen)
{
struct afs_volume *volume;
struct afs_fs_context fc = {
.type = 0, /* Explicitly leave it to the VLDB */
.volnamesz = namelen,
.volname = name,
.net = cell->net,
.cell = cell,
.key = key, /* This might need to be something */
};
volume = afs_create_volume(&fc);
_leave(" = %px", volume);
return volume;
}
/*
* Compare two addresses.
*/
static int afs_compare_addrs(const struct sockaddr_rxrpc *srx_a,
const struct sockaddr_rxrpc *srx_b)
{
short port_a, port_b;
int addr_a, addr_b, diff;
diff = (short)srx_a->transport_type - (short)srx_b->transport_type;
if (diff)
goto out;
switch (srx_a->transport_type) {
case AF_INET: {
const struct sockaddr_in *a = &srx_a->transport.sin;
const struct sockaddr_in *b = &srx_b->transport.sin;
addr_a = ntohl(a->sin_addr.s_addr);
addr_b = ntohl(b->sin_addr.s_addr);
diff = addr_a - addr_b;
if (diff == 0) {
port_a = ntohs(a->sin_port);
port_b = ntohs(b->sin_port);
diff = port_a - port_b;
}
break;
}
case AF_INET6: {
const struct sockaddr_in6 *a = &srx_a->transport.sin6;
const struct sockaddr_in6 *b = &srx_b->transport.sin6;
diff = memcmp(&a->sin6_addr, &b->sin6_addr, 16);
if (diff == 0) {
port_a = ntohs(a->sin6_port);
port_b = ntohs(b->sin6_port);
diff = port_a - port_b;
}
break;
}
default:
BUG();
}
out:
return diff;
}
/*
* Compare the address lists of a pair of fileservers.
*/
static int afs_compare_fs_alists(const struct afs_server *server_a,
const struct afs_server *server_b)
{
const struct afs_addr_list *la, *lb;
int a = 0, b = 0, addr_matches = 0;
la = rcu_dereference(server_a->addresses);
lb = rcu_dereference(server_b->addresses);
while (a < la->nr_addrs && b < lb->nr_addrs) {
const struct sockaddr_rxrpc *srx_a = &la->addrs[a];
const struct sockaddr_rxrpc *srx_b = &lb->addrs[b];
int diff = afs_compare_addrs(srx_a, srx_b);
if (diff < 0) {
a++;
} else if (diff > 0) {
b++;
} else {
addr_matches++;
a++;
b++;
}
}
return addr_matches;
}
/*
* Compare the fileserver lists of two volumes. The server lists are sorted in
* order of ascending UUID.
*/
static int afs_compare_volume_slists(const struct afs_volume *vol_a,
const struct afs_volume *vol_b)
{
const struct afs_server_list *la, *lb;
int i, a = 0, b = 0, uuid_matches = 0, addr_matches = 0;
la = rcu_dereference(vol_a->servers);
lb = rcu_dereference(vol_b->servers);
for (i = 0; i < AFS_MAXTYPES; i++)
if (la->vids[i] != lb->vids[i])
return 0;
while (a < la->nr_servers && b < lb->nr_servers) {
const struct afs_server *server_a = la->servers[a].server;
const struct afs_server *server_b = lb->servers[b].server;
int diff = memcmp(&server_a->uuid, &server_b->uuid, sizeof(uuid_t));
if (diff < 0) {
a++;
} else if (diff > 0) {
b++;
} else {
uuid_matches++;
addr_matches += afs_compare_fs_alists(server_a, server_b);
a++;
b++;
}
}
_leave(" = %d [um %d]", addr_matches, uuid_matches);
return addr_matches;
}
/*
* Compare root.cell volumes.
*/
static int afs_compare_cell_roots(struct afs_cell *cell)
{
struct afs_cell *p;
_enter("");
rcu_read_lock();
hlist_for_each_entry_rcu(p, &cell->net->proc_cells, proc_link) {
if (p == cell || p->alias_of)
continue;
if (!p->root_volume)
continue; /* Ignore cells that don't have a root.cell volume. */
if (afs_compare_volume_slists(cell->root_volume, p->root_volume) != 0)
goto is_alias;
}
rcu_read_unlock();
_leave(" = 0");
return 0;
is_alias:
rcu_read_unlock();
cell->alias_of = afs_get_cell(p);
return 1;
}
static int afs_do_cell_detect_alias(struct afs_cell *cell, struct key *key)
{
struct afs_volume *root_volume;
_enter("%s", cell->name);
/* Try and get the root.cell volume for comparison with other cells */
root_volume = afs_sample_volume(cell, key, "root.cell", 9);
if (!IS_ERR(root_volume)) {
cell->root_volume = root_volume;
return afs_compare_cell_roots(cell);
}
if (PTR_ERR(root_volume) != -ENOMEDIUM)
return PTR_ERR(root_volume);
/* Okay, this cell doesn't have an root.cell volume. We need to
* locate some other random volume and use that to check.
*/
return -ENOMEDIUM;
}
/*
* Check to see if a new cell is an alias of a cell we already have. At this
* point we have the cell's volume server list.
*
* Returns 0 if we didn't detect an alias, 1 if we found an alias and an error
* if we had problems gathering the data required. In the case the we did
* detect an alias, cell->alias_of is set to point to the assumed master.
*/
int afs_cell_detect_alias(struct afs_cell *cell, struct key *key)
{
struct afs_net *net = cell->net;
int ret;
if (mutex_lock_interruptible(&net->cells_alias_lock) < 0)
return -ERESTARTSYS;
if (test_bit(AFS_CELL_FL_CHECK_ALIAS, &cell->flags)) {
ret = afs_do_cell_detect_alias(cell, key);
if (ret >= 0)
clear_bit_unlock(AFS_CELL_FL_CHECK_ALIAS, &cell->flags);
} else {
ret = cell->alias_of ? 1 : 0;
}
mutex_unlock(&net->cells_alias_lock);
if (ret == 1)
pr_notice("kAFS: Cell %s is an alias of %s\n",
cell->name, cell->alias_of->name);
return ret;
}
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