// SPDX-License-Identifier: GPL-2.0-or-later
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/* AFS cell alias detection
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*
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* Copyright (C) 2020 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/namei.h>
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#include <keys/rxrpc-type.h>
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#include "internal.h"
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/*
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* Sample a volume.
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*/
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static struct afs_volume *afs_sample_volume(struct afs_cell *cell, struct key *key,
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const char *name, unsigned int namelen)
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{
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struct afs_volume *volume;
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struct afs_fs_context fc = {
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.type = 0, /* Explicitly leave it to the VLDB */
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.volnamesz = namelen,
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.volname = name,
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.net = cell->net,
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.cell = cell,
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.key = key, /* This might need to be something */
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};
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volume = afs_create_volume(&fc);
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_leave(" = %p", volume);
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return volume;
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}
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/*
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* Compare two addresses.
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*/
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static int afs_compare_addrs(const struct sockaddr_rxrpc *srx_a,
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const struct sockaddr_rxrpc *srx_b)
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{
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short port_a, port_b;
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int addr_a, addr_b, diff;
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diff = (short)srx_a->transport_type - (short)srx_b->transport_type;
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if (diff)
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goto out;
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switch (srx_a->transport_type) {
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case AF_INET: {
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const struct sockaddr_in *a = &srx_a->transport.sin;
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const struct sockaddr_in *b = &srx_b->transport.sin;
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addr_a = ntohl(a->sin_addr.s_addr);
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addr_b = ntohl(b->sin_addr.s_addr);
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diff = addr_a - addr_b;
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if (diff == 0) {
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port_a = ntohs(a->sin_port);
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port_b = ntohs(b->sin_port);
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diff = port_a - port_b;
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}
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break;
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}
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case AF_INET6: {
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const struct sockaddr_in6 *a = &srx_a->transport.sin6;
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const struct sockaddr_in6 *b = &srx_b->transport.sin6;
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diff = memcmp(&a->sin6_addr, &b->sin6_addr, 16);
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if (diff == 0) {
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port_a = ntohs(a->sin6_port);
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port_b = ntohs(b->sin6_port);
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diff = port_a - port_b;
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}
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break;
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}
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default:
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WARN_ON(1);
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diff = 1;
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}
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out:
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return diff;
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}
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/*
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* Compare the address lists of a pair of fileservers.
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*/
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static int afs_compare_fs_alists(const struct afs_server *server_a,
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const struct afs_server *server_b)
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{
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const struct afs_addr_list *la, *lb;
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int a = 0, b = 0, addr_matches = 0;
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la = rcu_dereference(server_a->addresses);
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lb = rcu_dereference(server_b->addresses);
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while (a < la->nr_addrs && b < lb->nr_addrs) {
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const struct sockaddr_rxrpc *srx_a = &la->addrs[a];
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const struct sockaddr_rxrpc *srx_b = &lb->addrs[b];
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int diff = afs_compare_addrs(srx_a, srx_b);
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if (diff < 0) {
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a++;
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} else if (diff > 0) {
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b++;
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} else {
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addr_matches++;
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a++;
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b++;
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}
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}
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return addr_matches;
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}
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/*
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* Compare the fileserver lists of two volumes. The server lists are sorted in
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* order of ascending UUID.
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*/
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static int afs_compare_volume_slists(const struct afs_volume *vol_a,
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const struct afs_volume *vol_b)
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{
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const struct afs_server_list *la, *lb;
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int i, a = 0, b = 0, uuid_matches = 0, addr_matches = 0;
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la = rcu_dereference(vol_a->servers);
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lb = rcu_dereference(vol_b->servers);
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for (i = 0; i < AFS_MAXTYPES; i++)
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if (la->vids[i] != lb->vids[i])
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return 0;
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while (a < la->nr_servers && b < lb->nr_servers) {
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const struct afs_server *server_a = la->servers[a].server;
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const struct afs_server *server_b = lb->servers[b].server;
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int diff = memcmp(&server_a->uuid, &server_b->uuid, sizeof(uuid_t));
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if (diff < 0) {
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a++;
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} else if (diff > 0) {
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b++;
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} else {
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uuid_matches++;
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addr_matches += afs_compare_fs_alists(server_a, server_b);
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a++;
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b++;
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}
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}
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_leave(" = %d [um %d]", addr_matches, uuid_matches);
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return addr_matches;
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}
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/*
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* Compare root.cell volumes.
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*/
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static int afs_compare_cell_roots(struct afs_cell *cell)
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{
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struct afs_cell *p;
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_enter("");
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rcu_read_lock();
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hlist_for_each_entry_rcu(p, &cell->net->proc_cells, proc_link) {
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if (p == cell || p->alias_of)
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continue;
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if (!p->root_volume)
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continue; /* Ignore cells that don't have a root.cell volume. */
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if (afs_compare_volume_slists(cell->root_volume, p->root_volume) != 0)
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goto is_alias;
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}
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rcu_read_unlock();
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_leave(" = 0");
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return 0;
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is_alias:
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rcu_read_unlock();
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cell->alias_of = afs_use_cell(p, afs_cell_trace_use_alias);
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return 1;
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}
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/*
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* Query the new cell for a volume from a cell we're already using.
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*/
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static int afs_query_for_alias_one(struct afs_cell *cell, struct key *key,
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struct afs_cell *p)
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{
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struct afs_volume *volume, *pvol = NULL;
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int ret;
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/* Arbitrarily pick a volume from the list. */
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read_seqlock_excl(&p->volume_lock);
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if (!RB_EMPTY_ROOT(&p->volumes))
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pvol = afs_get_volume(rb_entry(p->volumes.rb_node,
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struct afs_volume, cell_node),
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afs_volume_trace_get_query_alias);
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read_sequnlock_excl(&p->volume_lock);
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if (!pvol)
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return 0;
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_enter("%s:%s", cell->name, pvol->name);
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/* And see if it's in the new cell. */
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volume = afs_sample_volume(cell, key, pvol->name, pvol->name_len);
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if (IS_ERR(volume)) {
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afs_put_volume(cell->net, pvol, afs_volume_trace_put_query_alias);
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if (PTR_ERR(volume) != -ENOMEDIUM)
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return PTR_ERR(volume);
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/* That volume is not in the new cell, so not an alias */
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return 0;
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}
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/* The new cell has a like-named volume also - compare volume ID,
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* server and address lists.
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*/
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ret = 0;
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if (pvol->vid == volume->vid) {
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rcu_read_lock();
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if (afs_compare_volume_slists(volume, pvol))
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ret = 1;
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rcu_read_unlock();
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}
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afs_put_volume(cell->net, volume, afs_volume_trace_put_query_alias);
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afs_put_volume(cell->net, pvol, afs_volume_trace_put_query_alias);
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return ret;
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}
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/*
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* Query the new cell for volumes we know exist in cells we're already using.
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*/
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static int afs_query_for_alias(struct afs_cell *cell, struct key *key)
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{
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struct afs_cell *p;
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_enter("%s", cell->name);
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if (mutex_lock_interruptible(&cell->net->proc_cells_lock) < 0)
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return -ERESTARTSYS;
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hlist_for_each_entry(p, &cell->net->proc_cells, proc_link) {
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if (p == cell || p->alias_of)
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continue;
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if (RB_EMPTY_ROOT(&p->volumes))
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continue;
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if (p->root_volume)
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continue; /* Ignore cells that have a root.cell volume. */
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afs_use_cell(p, afs_cell_trace_use_check_alias);
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mutex_unlock(&cell->net->proc_cells_lock);
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if (afs_query_for_alias_one(cell, key, p) != 0)
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goto is_alias;
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if (mutex_lock_interruptible(&cell->net->proc_cells_lock) < 0) {
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afs_unuse_cell(cell->net, p, afs_cell_trace_unuse_check_alias);
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return -ERESTARTSYS;
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}
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afs_unuse_cell(cell->net, p, afs_cell_trace_unuse_check_alias);
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}
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mutex_unlock(&cell->net->proc_cells_lock);
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_leave(" = 0");
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return 0;
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is_alias:
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cell->alias_of = p; /* Transfer our ref */
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return 1;
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}
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/*
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* Look up a VLDB record for a volume.
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*/
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static char *afs_vl_get_cell_name(struct afs_cell *cell, struct key *key)
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{
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struct afs_vl_cursor vc;
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char *cell_name = ERR_PTR(-EDESTADDRREQ);
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bool skipped = false, not_skipped = false;
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int ret;
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if (!afs_begin_vlserver_operation(&vc, cell, key))
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return ERR_PTR(-ERESTARTSYS);
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while (afs_select_vlserver(&vc)) {
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if (!test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags)) {
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vc.ac.error = -EOPNOTSUPP;
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skipped = true;
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continue;
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}
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not_skipped = true;
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cell_name = afs_yfsvl_get_cell_name(&vc);
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}
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ret = afs_end_vlserver_operation(&vc);
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if (skipped && !not_skipped)
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ret = -EOPNOTSUPP;
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return ret < 0 ? ERR_PTR(ret) : cell_name;
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}
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static int yfs_check_canonical_cell_name(struct afs_cell *cell, struct key *key)
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{
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struct afs_cell *master;
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char *cell_name;
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cell_name = afs_vl_get_cell_name(cell, key);
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if (IS_ERR(cell_name))
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return PTR_ERR(cell_name);
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if (strcmp(cell_name, cell->name) == 0) {
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kfree(cell_name);
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return 0;
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}
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master = afs_lookup_cell(cell->net, cell_name, strlen(cell_name),
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NULL, false);
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kfree(cell_name);
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if (IS_ERR(master))
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return PTR_ERR(master);
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cell->alias_of = master; /* Transfer our ref */
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return 1;
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}
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static int afs_do_cell_detect_alias(struct afs_cell *cell, struct key *key)
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{
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struct afs_volume *root_volume;
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int ret;
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_enter("%s", cell->name);
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ret = yfs_check_canonical_cell_name(cell, key);
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if (ret != -EOPNOTSUPP)
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return ret;
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/* Try and get the root.cell volume for comparison with other cells */
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root_volume = afs_sample_volume(cell, key, "root.cell", 9);
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if (!IS_ERR(root_volume)) {
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cell->root_volume = root_volume;
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return afs_compare_cell_roots(cell);
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}
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if (PTR_ERR(root_volume) != -ENOMEDIUM)
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return PTR_ERR(root_volume);
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/* Okay, this cell doesn't have an root.cell volume. We need to
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* locate some other random volume and use that to check.
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*/
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return afs_query_for_alias(cell, key);
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}
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/*
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* Check to see if a new cell is an alias of a cell we already have. At this
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* point we have the cell's volume server list.
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*
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* Returns 0 if we didn't detect an alias, 1 if we found an alias and an error
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* if we had problems gathering the data required. In the case the we did
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* detect an alias, cell->alias_of is set to point to the assumed master.
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*/
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int afs_cell_detect_alias(struct afs_cell *cell, struct key *key)
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{
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struct afs_net *net = cell->net;
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int ret;
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if (mutex_lock_interruptible(&net->cells_alias_lock) < 0)
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return -ERESTARTSYS;
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if (test_bit(AFS_CELL_FL_CHECK_ALIAS, &cell->flags)) {
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ret = afs_do_cell_detect_alias(cell, key);
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if (ret >= 0)
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clear_bit_unlock(AFS_CELL_FL_CHECK_ALIAS, &cell->flags);
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} else {
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ret = cell->alias_of ? 1 : 0;
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}
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mutex_unlock(&net->cells_alias_lock);
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if (ret == 1)
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pr_notice("kAFS: Cell %s is an alias of %s\n",
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cell->name, cell->alias_of->name);
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return ret;
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}
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