// 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
  ", 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;
  }