// SPDX-License-Identifier: GPL-2.0-or-later
/* Server address list management
 *
 * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/dns_resolver.h>
#include <linux/inet.h>
#include <keys/rxrpc-type.h>
#include "internal.h"
#include "afs_fs.h"

/*
 * Release an address list.
 */
void afs_put_addrlist(struct afs_addr_list *alist)
{
        if (alist && refcount_dec_and_test(&alist->usage))
                kfree_rcu(alist, rcu);
}

/*
 * Allocate an address list.
 */
struct afs_addr_list *afs_alloc_addrlist(unsigned int nr,
                                         unsigned short service,
                                         unsigned short port)
{
        struct afs_addr_list *alist;
        unsigned int i;

        _enter("%u,%u,%u", nr, service, port);

        if (nr > AFS_MAX_ADDRESSES)
                nr = AFS_MAX_ADDRESSES;

        alist = kzalloc(struct_size(alist, addrs, nr), GFP_KERNEL);
        if (!alist)
                return NULL;

        refcount_set(&alist->usage, 1);
        alist->max_addrs = nr;

        for (i = 0; i < nr; i++) {
                struct sockaddr_rxrpc *srx = &alist->addrs[i];
                srx->srx_family                 = AF_RXRPC;
                srx->srx_service                = service;
                srx->transport_type             = SOCK_DGRAM;
                srx->transport_len              = sizeof(srx->transport.sin6);
                srx->transport.sin6.sin6_family = AF_INET6;
                srx->transport.sin6.sin6_port   = htons(port);
        }

        return alist;
}

/*
 * Parse a text string consisting of delimited addresses.
 */
struct afs_vlserver_list *afs_parse_text_addrs(struct afs_net *net,
                                               const char *text, size_t len,
                                               char delim,
                                               unsigned short service,
                                               unsigned short port)
{
        struct afs_vlserver_list *vllist;
        struct afs_addr_list *alist;
        const char *p, *end = text + len;
        const char *problem;
        unsigned int nr = 0;
        int ret = -ENOMEM;

        _enter("%*.*s,%c", (int)len, (int)len, text, delim);

        if (!len) {
                _leave(" = -EDESTADDRREQ [empty]");
                return ERR_PTR(-EDESTADDRREQ);
        }

        if (delim == ':' && (memchr(text, ',', len) || !memchr(text, '.', len)))
                delim = ',';

        /* Count the addresses */
        p = text;
        do {
                if (!*p) {
                        problem = "nul";
                        goto inval;
                }
                if (*p == delim)
                        continue;
                nr++;
                if (*p == '[') {
                        p++;
                        if (p == end) {
                                problem = "brace1";
                                goto inval;
                        }
                        p = memchr(p, ']', end - p);
                        if (!p) {
                                problem = "brace2";
                                goto inval;
                        }
                        p++;
                        if (p >= end)
                                break;
                }

                p = memchr(p, delim, end - p);
                if (!p)
                        break;
                p++;
        } while (p < end);

        _debug("%u/%u addresses", nr, AFS_MAX_ADDRESSES);

        vllist = afs_alloc_vlserver_list(1);
        if (!vllist)
                return ERR_PTR(-ENOMEM);

        vllist->nr_servers = 1;
        vllist->servers[0].server = afs_alloc_vlserver("<dummy>", 7, AFS_VL_PORT);
        if (!vllist->servers[0].server)
                goto error_vl;

        alist = afs_alloc_addrlist(nr, service, AFS_VL_PORT);
        if (!alist)
                goto error;

        /* Extract the addresses */
        p = text;
        do {
                const char *q, *stop;
                unsigned int xport = port;
                __be32 x[4];
                int family;

                if (*p == delim) {
                        p++;
                        continue;
                }

                if (*p == '[') {
                        p++;
                        q = memchr(p, ']', end - p);
                } else {
                        for (q = p; q < end; q++)
                                if (*q == '+' || *q == delim)
                                        break;
                }

                if (in4_pton(p, q - p, (u8 *)&x[0], -1, &stop)) {
                        family = AF_INET;
                } else if (in6_pton(p, q - p, (u8 *)x, -1, &stop)) {
                        family = AF_INET6;
                } else {
                        problem = "family";
                        goto bad_address;
                }

                p = q;
                if (stop != p) {
                        problem = "nostop";
                        goto bad_address;
                }

                if (q < end && *q == ']')
                        p++;

                if (p < end) {
                        if (*p == '+') {
                                /* Port number specification "+1234" */
                                xport = 0;
                                p++;
                                if (p >= end || !isdigit(*p)) {
                                        problem = "port";
                                        goto bad_address;
                                }
                                do {
                                        xport *= 10;
                                        xport += *p - '0';
                                        if (xport > 65535) {
                                                problem = "pval";
                                                goto bad_address;
                                        }
                                        p++;
                                } while (p < end && isdigit(*p));
                        } else if (*p == delim) {
                                p++;
                        } else {
                                problem = "weird";
                                goto bad_address;
                        }
                }

                if (family == AF_INET)
                        afs_merge_fs_addr4(alist, x[0], xport);
                else
                        afs_merge_fs_addr6(alist, x, xport);

        } while (p < end);

        rcu_assign_pointer(vllist->servers[0].server->addresses, alist);
        _leave(" = [nr %u]", alist->nr_addrs);
        return vllist;

inval:
        _leave(" = -EINVAL [%s %zu %*.*s]",
               problem, p - text, (int)len, (int)len, text);
        return ERR_PTR(-EINVAL);
bad_address:
        _leave(" = -EINVAL [%s %zu %*.*s]",
               problem, p - text, (int)len, (int)len, text);
        ret = -EINVAL;
error:
        afs_put_addrlist(alist);
error_vl:
        afs_put_vlserverlist(net, vllist);
        return ERR_PTR(ret);
}

/*
 * Compare old and new address lists to see if there's been any change.
 * - How to do this in better than O(Nlog(N)) time?
 *   - We don't really want to sort the address list, but would rather take the
 *     list as we got it so as not to undo record rotation by the DNS server.
 */
#if 0
static int afs_cmp_addr_list(const struct afs_addr_list *a1,
                             const struct afs_addr_list *a2)
{
}
#endif

/*
 * Perform a DNS query for VL servers and build a up an address list.
 */
struct afs_vlserver_list *afs_dns_query(struct afs_cell *cell, time64_t *_expiry)
{
        struct afs_vlserver_list *vllist;
        char *result = NULL;
        int ret;

        _enter("%s", cell->name);

        ret = dns_query(cell->net->net, "afsdb", cell->name, cell->name_len,
                        "srv=1", &result, _expiry, true);
        if (ret < 0) {
                _leave(" = %d [dns]", ret);
                return ERR_PTR(ret);
        }

        if (*_expiry == 0)
                *_expiry = ktime_get_real_seconds() + 60;

        if (ret > 1 && result[0] == 0)
                vllist = afs_extract_vlserver_list(cell, result, ret);
        else
                vllist = afs_parse_text_addrs(cell->net, result, ret, ',',
                                              VL_SERVICE, AFS_VL_PORT);
        kfree(result);
        if (IS_ERR(vllist) && vllist != ERR_PTR(-ENOMEM))
                pr_err("Failed to parse DNS data %ld\n", PTR_ERR(vllist));

        return vllist;
}

/*
 * Merge an IPv4 entry into a fileserver address list.
 */
void afs_merge_fs_addr4(struct afs_addr_list *alist, __be32 xdr, u16 port)
{
        struct sockaddr_rxrpc *srx;
        u32 addr = ntohl(xdr);
        int i;

        if (alist->nr_addrs >= alist->max_addrs)
                return;

        for (i = 0; i < alist->nr_ipv4; i++) {
                struct sockaddr_in *a = &alist->addrs[i].transport.sin;
                u32 a_addr = ntohl(a->sin_addr.s_addr);
                u16 a_port = ntohs(a->sin_port);

                if (addr == a_addr && port == a_port)
                        return;
                if (addr == a_addr && port < a_port)
                        break;
                if (addr < a_addr)
                        break;
        }

        if (i < alist->nr_addrs)
                memmove(alist->addrs + i + 1,
                        alist->addrs + i,
                        sizeof(alist->addrs[0]) * (alist->nr_addrs - i));

        srx = &alist->addrs[i];
        srx->srx_family = AF_RXRPC;
        srx->transport_type = SOCK_DGRAM;
        srx->transport_len = sizeof(srx->transport.sin);
        srx->transport.sin.sin_family = AF_INET;
        srx->transport.sin.sin_port = htons(port);
        srx->transport.sin.sin_addr.s_addr = xdr;
        alist->nr_ipv4++;
        alist->nr_addrs++;
}

/*
 * Merge an IPv6 entry into a fileserver address list.
 */
void afs_merge_fs_addr6(struct afs_addr_list *alist, __be32 *xdr, u16 port)
{
        struct sockaddr_rxrpc *srx;
        int i, diff;

        if (alist->nr_addrs >= alist->max_addrs)
                return;

        for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
                struct sockaddr_in6 *a = &alist->addrs[i].transport.sin6;
                u16 a_port = ntohs(a->sin6_port);

                diff = memcmp(xdr, &a->sin6_addr, 16);
                if (diff == 0 && port == a_port)
                        return;
                if (diff == 0 && port < a_port)
                        break;
                if (diff < 0)
                        break;
        }

        if (i < alist->nr_addrs)
                memmove(alist->addrs + i + 1,
                        alist->addrs + i,
                        sizeof(alist->addrs[0]) * (alist->nr_addrs - i));

        srx = &alist->addrs[i];
        srx->srx_family = AF_RXRPC;
        srx->transport_type = SOCK_DGRAM;
        srx->transport_len = sizeof(srx->transport.sin6);
        srx->transport.sin6.sin6_family = AF_INET6;
        srx->transport.sin6.sin6_port = htons(port);
        memcpy(&srx->transport.sin6.sin6_addr, xdr, 16);
        alist->nr_addrs++;
}

/*
 * Get an address to try.
 */
bool afs_iterate_addresses(struct afs_addr_cursor *ac)
{
        unsigned long set, failed;
        int index;

        if (!ac->alist)
                return false;

        set = ac->alist->responded;
        failed = ac->alist->failed;
        _enter("%lx-%lx-%lx,%d", set, failed, ac->tried, ac->index);

        ac->nr_iterations++;

        set &= ~(failed | ac->tried);

        if (!set)
                return false;

        index = READ_ONCE(ac->alist->preferred);
        if (test_bit(index, &set))
                goto selected;

        index = __ffs(set);

selected:
        ac->index = index;
        set_bit(index, &ac->tried);
        ac->responded = false;
        return true;
}

/*
 * Release an address list cursor.
 */
int afs_end_cursor(struct afs_addr_cursor *ac)
{
        struct afs_addr_list *alist;

        alist = ac->alist;
        if (alist) {
                if (ac->responded &&
                    ac->index != alist->preferred &&
                    test_bit(ac->alist->preferred, &ac->tried))
                        WRITE_ONCE(alist->preferred, ac->index);
                afs_put_addrlist(alist);
                ac->alist = NULL;
        }

        return ac->error;
}