net/netfilter/ipvs/ip_vs_ftp.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * ip_vs_ftp.c: IPVS ftp application module
   4  *
   5  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   6  *
   7  * Changes:
   8  *
   9  * Most code here is taken from ip_masq_ftp.c in kernel 2.2. The difference
  10  * is that ip_vs_ftp module handles the reverse direction to ip_masq_ftp.
  11  *
  12  *              IP_MASQ_FTP ftp masquerading module
  13  *
  14  * Version:     @(#)ip_masq_ftp.c 0.04   02/05/96
  15  *
  16  * Author:      Wouter Gadeyne
  17  */
  18
  19 #define KMSG_COMPONENT "IPVS"
  20 #define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
  21
  22 #include <linux/module.h>
  23 #include <linux/moduleparam.h>
  24 #include <linux/kernel.h>
  25 #include <linux/skbuff.h>
  26 #include <linux/ctype.h>
  27 #include <linux/inet.h>
  28 #include <linux/in.h>
  29 #include <linux/ip.h>
  30 #include <linux/netfilter.h>
  31 #include <net/netfilter/nf_conntrack.h>
  32 #include <net/netfilter/nf_conntrack_expect.h>
  33 #include <net/netfilter/nf_nat.h>
  34 #include <net/netfilter/nf_nat_helper.h>
  35 #include <linux/gfp.h>
  36 #include <net/protocol.h>
  37 #include <net/tcp.h>
  38 #include <asm/unaligned.h>
  39
  40 #include <net/ip_vs.h>
  41
  42
  43 #define SERVER_STRING_PASV "227 "
  44 #define CLIENT_STRING_PORT "PORT"
  45 #define SERVER_STRING_EPSV "229 "
  46 #define CLIENT_STRING_EPRT "EPRT"
  47
  48 enum {
  49         IP_VS_FTP_ACTIVE = 0,
  50         IP_VS_FTP_PORT = 0,
  51         IP_VS_FTP_PASV,
  52         IP_VS_FTP_EPRT,
  53         IP_VS_FTP_EPSV,
  54 };
  55
  56 /*
  57  * List of ports (up to IP_VS_APP_MAX_PORTS) to be handled by helper
  58  * First port is set to the default port.
  59  */
  60 static unsigned int ports_count = 1;
  61 static unsigned short ports[IP_VS_APP_MAX_PORTS] = {21, 0};
  62 module_param_array(ports, ushort, &ports_count, 0444);
  63 MODULE_PARM_DESC(ports, "Ports to monitor for FTP control commands");
  64
  65
  66 static char *ip_vs_ftp_data_ptr(struct sk_buff *skb, struct ip_vs_iphdr *ipvsh)
  67 {
  68         struct tcphdr *th = (struct tcphdr *)((char *)skb->data + ipvsh->len);
  69
  70         if ((th->doff << 2) < sizeof(struct tcphdr))
  71                 return NULL;
  72
  73         return (char *)th + (th->doff << 2);
  74 }
  75
  76 static int
  77 ip_vs_ftp_init_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  78 {
  79         /* We use connection tracking for the command connection */
  80         cp->flags |= IP_VS_CONN_F_NFCT;
  81         return 0;
  82 }
  83
  84
  85 static int
  86 ip_vs_ftp_done_conn(struct ip_vs_app *app, struct ip_vs_conn *cp)
  87 {
  88         return 0;
  89 }
  90
  91
  92 /* Get <addr,port> from the string "xxx.xxx.xxx.xxx,ppp,ppp", started
  93  * with the "pattern". <addr,port> is in network order.
  94  * Parse extended format depending on ext. In this case addr can be pre-set.
  95  */
  96 static int ip_vs_ftp_get_addrport(char *data, char *data_limit,
  97                                   const char *pattern, size_t plen,
  98                                   char skip, bool ext, int mode,
  99                                   union nf_inet_addr *addr, __be16 *port,
 100                                   __u16 af, char **start, char **end)
 101 {
 102         char *s, c;
 103         unsigned char p[6];
 104         char edelim;
 105         __u16 hport;
 106         int i = 0;
 107
 108         if (data_limit - data < plen) {
 109                 /* check if there is partial match */
 110                 if (strncasecmp(data, pattern, data_limit - data) == 0)
 111                         return -1;
 112                 else
 113                         return 0;
 114         }
 115
 116         if (strncasecmp(data, pattern, plen) != 0) {
 117                 return 0;
 118         }
 119         s = data + plen;
 120         if (skip) {
 121                 bool found = false;
 122
 123                 for (;; s++) {
 124                         if (s == data_limit)
 125                                 return -1;
 126                         if (!found) {
 127                                 /* "(" is optional for non-extended format,
 128                                  * so catch the start of IPv4 address
 129                                  */
 130                                 if (!ext && isdigit(*s))
 131                                         break;
 132                                 if (*s == skip)
 133                                         found = true;
 134                         } else if (*s != skip) {
 135                                 break;
 136                         }
 137                 }
 138         }
 139         /* Old IPv4-only format? */
 140         if (!ext) {
 141                 p[0] = 0;
 142                 for (data = s; ; data++) {
 143                         if (data == data_limit)
 144                                 return -1;
 145                         c = *data;
 146                         if (isdigit(c)) {
 147                                 p[i] = p[i]*10 + c - '0';
 148                         } else if (c == ',' && i < 5) {
 149                                 i++;
 150                                 p[i] = 0;
 151                         } else {
 152                                 /* unexpected character or terminator */
 153                                 break;
 154                         }
 155                 }
 156
 157                 if (i != 5)
 158                         return -1;
 159
 160                 *start = s;
 161                 *end = data;
 162                 addr->ip = get_unaligned((__be32 *) p);
 163                 *port = get_unaligned((__be16 *) (p + 4));
 164                 return 1;
 165         }
 166         if (s == data_limit)
 167                 return -1;
 168         *start = s;
 169         edelim = *s++;
 170         if (edelim < 33 || edelim > 126)
 171                 return -1;
 172         if (s == data_limit)
 173                 return -1;
 174         if (*s == edelim) {
 175                 /* Address family is usually missing for EPSV response */
 176                 if (mode != IP_VS_FTP_EPSV)
 177                         return -1;
 178                 s++;
 179                 if (s == data_limit)
 180                         return -1;
 181                 /* Then address should be missing too */
 182                 if (*s != edelim)
 183                         return -1;
 184                 /* Caller can pre-set addr, if needed */
 185                 s++;
 186         } else {
 187                 const char *ep;
 188
 189                 /* We allow address only from same family */
 190                 if (af == AF_INET6 && *s != '2')
 191                         return -1;
 192                 if (af == AF_INET && *s != '1')
 193                         return -1;
 194                 s++;
 195                 if (s == data_limit)
 196                         return -1;
 197                 if (*s != edelim)
 198                         return -1;
 199                 s++;
 200                 if (s == data_limit)
 201                         return -1;
 202                 if (af == AF_INET6) {
 203                         if (in6_pton(s, data_limit - s, (u8 *)addr, edelim,
 204                                      &ep) <= 0)
 205                                 return -1;
 206                 } else {
 207                         if (in4_pton(s, data_limit - s, (u8 *)addr, edelim,
 208                                      &ep) <= 0)
 209                                 return -1;
 210                 }
 211                 s = (char *) ep;
 212                 if (s == data_limit)
 213                         return -1;
 214                 if (*s != edelim)
 215                         return -1;
 216                 s++;
 217         }
 218         for (hport = 0; ; s++)
 219         {
 220                 if (s == data_limit)
 221                         return -1;
 222                 if (!isdigit(*s))
 223                         break;
 224                 hport = hport * 10 + *s - '0';
 225         }
 226         if (s == data_limit || !hport || *s != edelim)
 227                 return -1;
 228         s++;
 229         *end = s;
 230         *port = htons(hport);
 231         return 1;
 232 }
 233
 234 /* Look at outgoing ftp packets to catch the response to a PASV/EPSV command
 235  * from the server (inside-to-outside).
 236  * When we see one, we build a connection entry with the client address,
 237  * client port 0 (unknown at the moment), the server address and the
 238  * server port.  Mark the current connection entry as a control channel
 239  * of the new entry. All this work is just to make the data connection
 240  * can be scheduled to the right server later.
 241  *
 242  * The outgoing packet should be something like
 243  *   "227 Entering Passive Mode (xxx,xxx,xxx,xxx,ppp,ppp)".
 244  * xxx,xxx,xxx,xxx is the server address, ppp,ppp is the server port number.
 245  * The extended format for EPSV response provides usually only port:
 246  *   "229 Entering Extended Passive Mode (|||ppp|)"
 247  */
 248 static int ip_vs_ftp_out(struct ip_vs_app *app, struct ip_vs_conn *cp,
 249                          struct sk_buff *skb, int *diff,
 250                          struct ip_vs_iphdr *ipvsh)
 251 {
 252         char *data, *data_limit;
 253         char *start, *end;
 254         union nf_inet_addr from;
 255         __be16 port;
 256         struct ip_vs_conn *n_cp;
 257         char buf[24];           /* xxx.xxx.xxx.xxx,ppp,ppp\000 */
 258         unsigned int buf_len;
 259         int ret = 0;
 260         enum ip_conntrack_info ctinfo;
 261         struct nf_conn *ct;
 262
 263         *diff = 0;
 264
 265         /* Only useful for established sessions */
 266         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 267                 return 1;
 268
 269         /* Linear packets are much easier to deal with. */
 270         if (skb_ensure_writable(skb, skb->len))
 271                 return 0;
 272
 273         if (cp->app_data == (void *) IP_VS_FTP_PASV) {
 274                 data = ip_vs_ftp_data_ptr(skb, ipvsh);
 275                 data_limit = skb_tail_pointer(skb);
 276
 277                 if (!data || data >= data_limit)
 278                         return 1;
 279
 280                 if (ip_vs_ftp_get_addrport(data, data_limit,
 281                                            SERVER_STRING_PASV,
 282                                            sizeof(SERVER_STRING_PASV)-1,
 283                                            '(', false, IP_VS_FTP_PASV,
 284                                            &from, &port, cp->af,
 285                                            &start, &end) != 1)
 286                         return 1;
 287
 288                 IP_VS_DBG(7, "PASV response (%pI4:%u) -> %pI4:%u detected\n",
 289                           &from.ip, ntohs(port), &cp->caddr.ip, 0);
 290         } else if (cp->app_data == (void *) IP_VS_FTP_EPSV) {
 291                 data = ip_vs_ftp_data_ptr(skb, ipvsh);
 292                 data_limit = skb_tail_pointer(skb);
 293
 294                 if (!data || data >= data_limit)
 295                         return 1;
 296
 297                 /* Usually, data address is not specified but
 298                  * we support different address, so pre-set it.
 299                  */
 300                 from = cp->daddr;
 301                 if (ip_vs_ftp_get_addrport(data, data_limit,
 302                                            SERVER_STRING_EPSV,
 303                                            sizeof(SERVER_STRING_EPSV)-1,
 304                                            '(', true, IP_VS_FTP_EPSV,
 305                                            &from, &port, cp->af,
 306                                            &start, &end) != 1)
 307                         return 1;
 308
 309                 IP_VS_DBG_BUF(7, "EPSV response (%s:%u) -> %s:%u detected\n",
 310                               IP_VS_DBG_ADDR(cp->af, &from), ntohs(port),
 311                               IP_VS_DBG_ADDR(cp->af, &cp->caddr), 0);
 312         } else {
 313                 return 1;
 314         }
 315
 316         /* Now update or create a connection entry for it */
 317         {
 318                 struct ip_vs_conn_param p;
 319
 320                 ip_vs_conn_fill_param(cp->ipvs, cp->af,
 321                                       ipvsh->protocol, &from, port,
 322                                       &cp->caddr, 0, &p);
 323                 n_cp = ip_vs_conn_out_get(&p);
 324         }
 325         if (!n_cp) {
 326                 struct ip_vs_conn_param p;
 327
 328                 ip_vs_conn_fill_param(cp->ipvs,
 329                                       cp->af, ipvsh->protocol, &cp->caddr,
 330                                       0, &cp->vaddr, port, &p);
 331                 n_cp = ip_vs_conn_new(&p, cp->af, &from, port,
 332                                       IP_VS_CONN_F_NO_CPORT |
 333                                       IP_VS_CONN_F_NFCT,
 334                                       cp->dest, skb->mark);
 335                 if (!n_cp)
 336                         return 0;
 337
 338                 /* add its controller */
 339                 ip_vs_control_add(n_cp, cp);
 340         }
 341
 342         /* Replace the old passive address with the new one */
 343         if (cp->app_data == (void *) IP_VS_FTP_PASV) {
 344                 from.ip = n_cp->vaddr.ip;
 345                 port = n_cp->vport;
 346                 snprintf(buf, sizeof(buf), "%u,%u,%u,%u,%u,%u",
 347                          ((unsigned char *)&from.ip)[0],
 348                          ((unsigned char *)&from.ip)[1],
 349                          ((unsigned char *)&from.ip)[2],
 350                          ((unsigned char *)&from.ip)[3],
 351                          ntohs(port) >> 8,
 352                          ntohs(port) & 0xFF);
 353         } else if (cp->app_data == (void *) IP_VS_FTP_EPSV) {
 354                 from = n_cp->vaddr;
 355                 port = n_cp->vport;
 356                 /* Only port, client will use VIP for the data connection */
 357                 snprintf(buf, sizeof(buf), "|||%u|",
 358                          ntohs(port));
 359         } else {
 360                 *buf = 0;
 361         }
 362         buf_len = strlen(buf);
 363
 364         ct = nf_ct_get(skb, &ctinfo);
 365         if (ct) {
 366                 bool mangled;
 367
 368                 /* If mangling fails this function will return 0
 369                  * which will cause the packet to be dropped.
 370                  * Mangling can only fail under memory pressure,
 371                  * hopefully it will succeed on the retransmitted
 372                  * packet.
 373                  */
 374                 mangled = nf_nat_mangle_tcp_packet(skb, ct, ctinfo,
 375                                                    ipvsh->len,
 376                                                    start - data,
 377                                                    end - start,
 378                                                    buf, buf_len);
 379                 if (mangled) {
 380                         ip_vs_nfct_expect_related(skb, ct, n_cp,
 381                                                   ipvsh->protocol, 0, 0);
 382                         if (skb->ip_summed == CHECKSUM_COMPLETE)
 383                                 skb->ip_summed = CHECKSUM_UNNECESSARY;
 384                         /* csum is updated */
 385                         ret = 1;
 386                 }
 387         }
 388
 389         /* Not setting 'diff' is intentional, otherwise the sequence
 390          * would be adjusted twice.
 391          */
 392
 393         cp->app_data = (void *) IP_VS_FTP_ACTIVE;
 394         ip_vs_tcp_conn_listen(n_cp);
 395         ip_vs_conn_put(n_cp);
 396         return ret;
 397 }
 398
 399
 400 /* Look at incoming ftp packets to catch the PASV/PORT/EPRT/EPSV command
 401  * (outside-to-inside).
 402  *
 403  * The incoming packet having the PORT command should be something like
 404  *      "PORT xxx,xxx,xxx,xxx,ppp,ppp\n".
 405  * xxx,xxx,xxx,xxx is the client address, ppp,ppp is the client port number.
 406  * In this case, we create a connection entry using the client address and
 407  * port, so that the active ftp data connection from the server can reach
 408  * the client.
 409  * Extended format:
 410  *      "EPSV\r\n" when client requests server address from same family
 411  *      "EPSV 1\r\n" when client requests IPv4 server address
 412  *      "EPSV 2\r\n" when client requests IPv6 server address
 413  *      "EPSV ALL\r\n" - not supported
 414  *      EPRT with specified delimiter (ASCII 33..126), "|" by default:
 415  *      "EPRT |1|IPv4ADDR|PORT|\r\n" when client provides IPv4 addrport
 416  *      "EPRT |2|IPv6ADDR|PORT|\r\n" when client provides IPv6 addrport
 417  */
 418 static int ip_vs_ftp_in(struct ip_vs_app *app, struct ip_vs_conn *cp,
 419                         struct sk_buff *skb, int *diff,
 420                         struct ip_vs_iphdr *ipvsh)
 421 {
 422         char *data, *data_start, *data_limit;
 423         char *start, *end;
 424         union nf_inet_addr to;
 425         __be16 port;
 426         struct ip_vs_conn *n_cp;
 427
 428         /* no diff required for incoming packets */
 429         *diff = 0;
 430
 431         /* Only useful for established sessions */
 432         if (cp->state != IP_VS_TCP_S_ESTABLISHED)
 433                 return 1;
 434
 435         /* Linear packets are much easier to deal with. */
 436         if (skb_ensure_writable(skb, skb->len))
 437                 return 0;
 438
 439         data = data_start = ip_vs_ftp_data_ptr(skb, ipvsh);
 440         data_limit = skb_tail_pointer(skb);
 441         if (!data || data >= data_limit)
 442                 return 1;
 443
 444         while (data <= data_limit - 6) {
 445                 if (cp->af == AF_INET &&
 446                     strncasecmp(data, "PASV\r\n", 6) == 0) {
 447                         /* Passive mode on */
 448                         IP_VS_DBG(7, "got PASV at %td of %td\n",
 449                                   data - data_start,
 450                                   data_limit - data_start);
 451                         cp->app_data = (void *) IP_VS_FTP_PASV;
 452                         return 1;
 453                 }
 454
 455                 /* EPSV or EPSV<space><net-prt> */
 456                 if (strncasecmp(data, "EPSV", 4) == 0 &&
 457                     (data[4] == ' ' || data[4] == '\r')) {
 458                         if (data[4] == ' ') {
 459                                 char proto = data[5];
 460
 461                                 if (data > data_limit - 7 || data[6] != '\r')
 462                                         return 1;
 463
 464 #ifdef CONFIG_IP_VS_IPV6
 465                                 if (cp->af == AF_INET6 && proto == '2') {
 466                                 } else
 467 #endif
 468                                 if (cp->af == AF_INET && proto == '1') {
 469                                 } else {
 470                                         return 1;
 471                                 }
 472                         }
 473                         /* Extended Passive mode on */
 474                         IP_VS_DBG(7, "got EPSV at %td of %td\n",
 475                                   data - data_start,
 476                                   data_limit - data_start);
 477                         cp->app_data = (void *) IP_VS_FTP_EPSV;
 478                         return 1;
 479                 }
 480
 481                 data++;
 482         }
 483
 484         /*
 485          * To support virtual FTP server, the scenerio is as follows:
 486          *       FTP client ----> Load Balancer ----> FTP server
 487          * First detect the port number in the application data,
 488          * then create a new connection entry for the coming data
 489          * connection.
 490          */
 491         if (cp->af == AF_INET &&
 492             ip_vs_ftp_get_addrport(data_start, data_limit,
 493                                    CLIENT_STRING_PORT,
 494                                    sizeof(CLIENT_STRING_PORT)-1,
 495                                    ' ', false, IP_VS_FTP_PORT,
 496                                    &to, &port, cp->af,
 497                                    &start, &end) == 1) {
 498
 499                 IP_VS_DBG(7, "PORT %pI4:%u detected\n", &to.ip, ntohs(port));
 500
 501                 /* Now update or create a connection entry for it */
 502                 IP_VS_DBG(7, "protocol %s %pI4:%u %pI4:%u\n",
 503                           ip_vs_proto_name(ipvsh->protocol),
 504                           &to.ip, ntohs(port), &cp->vaddr.ip,
 505                           ntohs(cp->vport)-1);
 506         } else if (ip_vs_ftp_get_addrport(data_start, data_limit,
 507                                           CLIENT_STRING_EPRT,
 508                                           sizeof(CLIENT_STRING_EPRT)-1,
 509                                           ' ', true, IP_VS_FTP_EPRT,
 510                                           &to, &port, cp->af,
 511                                           &start, &end) == 1) {
 512
 513                 IP_VS_DBG_BUF(7, "EPRT %s:%u detected\n",
 514                               IP_VS_DBG_ADDR(cp->af, &to), ntohs(port));
 515
 516                 /* Now update or create a connection entry for it */
 517                 IP_VS_DBG_BUF(7, "protocol %s %s:%u %s:%u\n",
 518                               ip_vs_proto_name(ipvsh->protocol),
 519                               IP_VS_DBG_ADDR(cp->af, &to), ntohs(port),
 520                               IP_VS_DBG_ADDR(cp->af, &cp->vaddr),
 521                               ntohs(cp->vport)-1);
 522         } else {
 523                 return 1;
 524         }
 525
 526         /* Passive mode off */
 527         cp->app_data = (void *) IP_VS_FTP_ACTIVE;
 528
 529         {
 530                 struct ip_vs_conn_param p;
 531                 ip_vs_conn_fill_param(cp->ipvs, cp->af,
 532                                       ipvsh->protocol, &to, port, &cp->vaddr,
 533                                       htons(ntohs(cp->vport)-1), &p);
 534                 n_cp = ip_vs_conn_in_get(&p);
 535                 if (!n_cp) {
 536                         n_cp = ip_vs_conn_new(&p, cp->af, &cp->daddr,
 537                                               htons(ntohs(cp->dport)-1),
 538                                               IP_VS_CONN_F_NFCT, cp->dest,
 539                                               skb->mark);
 540                         if (!n_cp)
 541                                 return 0;
 542
 543                         /* add its controller */
 544                         ip_vs_control_add(n_cp, cp);
 545                 }
 546         }
 547
 548         /*
 549          *      Move tunnel to listen state
 550          */
 551         ip_vs_tcp_conn_listen(n_cp);
 552         ip_vs_conn_put(n_cp);
 553
 554         return 1;
 555 }
 556
 557
 558 static struct ip_vs_app ip_vs_ftp = {
 559         .name =         "ftp",
 560         .type =         IP_VS_APP_TYPE_FTP,
 561         .protocol =     IPPROTO_TCP,
 562         .module =       THIS_MODULE,
 563         .incs_list =    LIST_HEAD_INIT(ip_vs_ftp.incs_list),
 564         .init_conn =    ip_vs_ftp_init_conn,
 565         .done_conn =    ip_vs_ftp_done_conn,
 566         .bind_conn =    NULL,
 567         .unbind_conn =  NULL,
 568         .pkt_out =      ip_vs_ftp_out,
 569         .pkt_in =       ip_vs_ftp_in,
 570 };
 571
 572 /*
 573  *      per netns ip_vs_ftp initialization
 574  */
 575 static int __net_init __ip_vs_ftp_init(struct net *net)
 576 {
 577         int i, ret;
 578         struct ip_vs_app *app;
 579         struct netns_ipvs *ipvs = net_ipvs(net);
 580
 581         if (!ipvs)
 582                 return -ENOENT;
 583
 584         app = register_ip_vs_app(ipvs, &ip_vs_ftp);
 585         if (IS_ERR(app))
 586                 return PTR_ERR(app);
 587
 588         for (i = 0; i < ports_count; i++) {
 589                 if (!ports[i])
 590                         continue;
 591                 ret = register_ip_vs_app_inc(ipvs, app, app->protocol, ports[i]);
 592                 if (ret)
 593                         goto err_unreg;
 594                 pr_info("%s: loaded support on port[%d] = %u\n",
 595                         app->name, i, ports[i]);
 596         }
 597         return 0;
 598
 599 err_unreg:
 600         unregister_ip_vs_app(ipvs, &ip_vs_ftp);
 601         return ret;
 602 }
 603 /*
 604  *      netns exit
 605  */
 606 static void __ip_vs_ftp_exit(struct net *net)
 607 {
 608         struct netns_ipvs *ipvs = net_ipvs(net);
 609
 610         if (!ipvs)
 611                 return;
 612
 613         unregister_ip_vs_app(ipvs, &ip_vs_ftp);
 614 }
 615
 616 static struct pernet_operations ip_vs_ftp_ops = {
 617         .init = __ip_vs_ftp_init,
 618         .exit = __ip_vs_ftp_exit,
 619 };
 620
 621 static int __init ip_vs_ftp_init(void)
 622 {
 623         /* rcu_barrier() is called by netns on error */
 624         return register_pernet_subsys(&ip_vs_ftp_ops);
 625 }
 626
 627 /*
 628  *      ip_vs_ftp finish.
 629  */
 630 static void __exit ip_vs_ftp_exit(void)
 631 {
 632         unregister_pernet_subsys(&ip_vs_ftp_ops);
 633         /* rcu_barrier() is called by netns */
 634 }
 635
 636
 637 module_init(ip_vs_ftp_init);
 638 module_exit(ip_vs_ftp_exit);
 639 MODULE_LICENSE("GPL");