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   1 /*
   2  * ip_vs_xmit.c: various packet transmitters for IPVS
   3  *
   4  * Version:     $Id: ip_vs_xmit.c,v 1.2 2002/11/30 01:50:35 wensong Exp $
   5  *
   6  * Authors:     Wensong Zhang <wensong@linuxvirtualserver.org>
   7  *              Julian Anastasov <ja@ssi.bg>
   8  *
   9  *              This program is free software; you can redistribute it and/or
  10  *              modify it under the terms of the GNU General Public License
  11  *              as published by the Free Software Foundation; either version
  12  *              2 of the License, or (at your option) any later version.
  13  *
  14  * Changes:
  15  *
  16  */
  17
  18 #include <linux/kernel.h>
  19 #include <linux/ip.h>
  20 #include <linux/tcp.h>                  /* for tcphdr */
  21 #include <net/tcp.h>                    /* for csum_tcpudp_magic */
  22 #include <net/udp.h>
  23 #include <net/icmp.h>                   /* for icmp_send */
  24 #include <net/route.h>                  /* for ip_route_output */
  25 #include <linux/netfilter.h>
  26 #include <linux/netfilter_ipv4.h>
  27
  28 #include <net/ip_vs.h>
  29
  30
  31 /*
  32  *      Destination cache to speed up outgoing route lookup
  33  */
  34 static inline void
  35 __ip_vs_dst_set(struct ip_vs_dest *dest, u32 rtos, struct dst_entry *dst)
  36 {
  37         struct dst_entry *old_dst;
  38
  39         old_dst = dest->dst_cache;
  40         dest->dst_cache = dst;
  41         dest->dst_rtos = rtos;
  42         dst_release(old_dst);
  43 }
  44
  45 static inline struct dst_entry *
  46 __ip_vs_dst_check(struct ip_vs_dest *dest, u32 rtos, u32 cookie)
  47 {
  48         struct dst_entry *dst = dest->dst_cache;
  49
  50         if (!dst)
  51                 return NULL;
  52         if ((dst->obsolete || rtos != dest->dst_rtos) &&
  53             dst->ops->check(dst, cookie) == NULL) {
  54                 dest->dst_cache = NULL;
  55                 dst_release(dst);
  56                 return NULL;
  57         }
  58         dst_hold(dst);
  59         return dst;
  60 }
  61
  62 static inline struct rtable *
  63 __ip_vs_get_out_rt(struct ip_vs_conn *cp, u32 rtos)
  64 {
  65         struct rtable *rt;                      /* Route to the other host */
  66         struct ip_vs_dest *dest = cp->dest;
  67
  68         if (dest) {
  69                 spin_lock(&dest->dst_lock);
  70                 if (!(rt = (struct rtable *)
  71                       __ip_vs_dst_check(dest, rtos, 0))) {
  72                         struct flowi fl = {
  73                                 .oif = 0,
  74                                 .nl_u = {
  75                                         .ip4_u = {
  76                                                 .daddr = dest->addr,
  77                                                 .saddr = 0,
  78                                                 .tos = rtos, } },
  79                         };
  80
  81                         if (ip_route_output_key(&rt, &fl)) {
  82                                 spin_unlock(&dest->dst_lock);
  83                                 IP_VS_DBG_RL("ip_route_output error, "
  84                                              "dest: %u.%u.%u.%u\n",
  85                                              NIPQUAD(dest->addr));
  86                                 return NULL;
  87                         }
  88                         __ip_vs_dst_set(dest, rtos, dst_clone(&rt->u.dst));
  89                         IP_VS_DBG(10, "new dst %u.%u.%u.%u, refcnt=%d, rtos=%X\n",
  90                                   NIPQUAD(dest->addr),
  91                                   atomic_read(&rt->u.dst.__refcnt), rtos);
  92                 }
  93                 spin_unlock(&dest->dst_lock);
  94         } else {
  95                 struct flowi fl = {
  96                         .oif = 0,
  97                         .nl_u = {
  98                                 .ip4_u = {
  99                                         .daddr = cp->daddr,
 100                                         .saddr = 0,
 101                                         .tos = rtos, } },
 102                 };
 103
 104                 if (ip_route_output_key(&rt, &fl)) {
 105                         IP_VS_DBG_RL("ip_route_output error, dest: "
 106                                      "%u.%u.%u.%u\n", NIPQUAD(cp->daddr));
 107                         return NULL;
 108                 }
 109         }
 110
 111         return rt;
 112 }
 113
 114
 115 /*
 116  *      Release dest->dst_cache before a dest is removed
 117  */
 118 void
 119 ip_vs_dst_reset(struct ip_vs_dest *dest)
 120 {
 121         struct dst_entry *old_dst;
 122
 123         old_dst = dest->dst_cache;
 124         dest->dst_cache = NULL;
 125         dst_release(old_dst);
 126 }
 127
 128 #define IP_VS_XMIT(skb, rt)                             \
 129 do {                                                    \
 130         (skb)->nfcache |= NFC_IPVS_PROPERTY;            \
 131         (skb)->ip_summed = CHECKSUM_NONE;               \
 132         NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, (skb), NULL,  \
 133                 (rt)->u.dst.dev, dst_output);           \
 134 } while (0)
 135
 136
 137 /*
 138  *      NULL transmitter (do nothing except return NF_ACCEPT)
 139  */
 140 int
 141 ip_vs_null_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 142                 struct ip_vs_protocol *pp)
 143 {
 144         /* we do not touch skb and do not need pskb ptr */
 145         return NF_ACCEPT;
 146 }
 147
 148
 149 /*
 150  *      Bypass transmitter
 151  *      Let packets bypass the destination when the destination is not
 152  *      available, it may be only used in transparent cache cluster.
 153  */
 154 int
 155 ip_vs_bypass_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 156                   struct ip_vs_protocol *pp)
 157 {
 158         struct rtable *rt;                      /* Route to the other host */
 159         struct iphdr  *iph = skb->nh.iph;
 160         u8     tos = iph->tos;
 161         int    mtu;
 162         struct flowi fl = {
 163                 .oif = 0,
 164                 .nl_u = {
 165                         .ip4_u = {
 166                                 .daddr = iph->daddr,
 167                                 .saddr = 0,
 168                                 .tos = RT_TOS(tos), } },
 169         };
 170
 171         EnterFunction(10);
 172
 173         if (ip_route_output_key(&rt, &fl)) {
 174                 IP_VS_DBG_RL("ip_vs_bypass_xmit(): ip_route_output error, "
 175                              "dest: %u.%u.%u.%u\n", NIPQUAD(iph->daddr));
 176                 goto tx_error_icmp;
 177         }
 178
 179         /* MTU checking */
 180         mtu = dst_mtu(&rt->u.dst);
 181         if ((skb->len > mtu) && (iph->frag_off&__constant_htons(IP_DF))) {
 182                 ip_rt_put(rt);
 183                 icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
 184                 IP_VS_DBG_RL("ip_vs_bypass_xmit(): frag needed\n");
 185                 goto tx_error;
 186         }
 187
 188         /*
 189          * Call ip_send_check because we are not sure it is called
 190          * after ip_defrag. Is copy-on-write needed?
 191          */
 192         if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
 193                 ip_rt_put(rt);
 194                 return NF_STOLEN;
 195         }
 196         ip_send_check(skb->nh.iph);
 197
 198         /* drop old route */
 199         dst_release(skb->dst);
 200         skb->dst = &rt->u.dst;
 201
 202         /* Another hack: avoid icmp_send in ip_fragment */
 203         skb->local_df = 1;
 204
 205         IP_VS_XMIT(skb, rt);
 206
 207         LeaveFunction(10);
 208         return NF_STOLEN;
 209
 210  tx_error_icmp:
 211         dst_link_failure(skb);
 212  tx_error:
 213         kfree_skb(skb);
 214         LeaveFunction(10);
 215         return NF_STOLEN;
 216 }
 217
 218
 219 /*
 220  *      NAT transmitter (only for outside-to-inside nat forwarding)
 221  *      Not used for related ICMP
 222  */
 223 int
 224 ip_vs_nat_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 225                struct ip_vs_protocol *pp)
 226 {
 227         struct rtable *rt;              /* Route to the other host */
 228         int mtu;
 229         struct iphdr *iph = skb->nh.iph;
 230
 231         EnterFunction(10);
 232
 233         /* check if it is a connection of no-client-port */
 234         if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT)) {
 235                 __u16 _pt, *p;
 236                 p = skb_header_pointer(skb, iph->ihl*4, sizeof(_pt), &_pt);
 237                 if (p == NULL)
 238                         goto tx_error;
 239                 ip_vs_conn_fill_cport(cp, *p);
 240                 IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
 241         }
 242
 243         if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
 244                 goto tx_error_icmp;
 245
 246         /* MTU checking */
 247         mtu = dst_mtu(&rt->u.dst);
 248         if ((skb->len > mtu) && (iph->frag_off&__constant_htons(IP_DF))) {
 249                 ip_rt_put(rt);
 250                 icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
 251                 IP_VS_DBG_RL_PKT(0, pp, skb, 0, "ip_vs_nat_xmit(): frag needed for");
 252                 goto tx_error;
 253         }
 254
 255         /* copy-on-write the packet before mangling it */
 256         if (!ip_vs_make_skb_writable(&skb, sizeof(struct iphdr)))
 257                 goto tx_error_put;
 258
 259         if (skb_cow(skb, rt->u.dst.dev->hard_header_len))
 260                 goto tx_error_put;
 261
 262         /* drop old route */
 263         dst_release(skb->dst);
 264         skb->dst = &rt->u.dst;
 265
 266         /* mangle the packet */
 267         if (pp->dnat_handler && !pp->dnat_handler(&skb, pp, cp))
 268                 goto tx_error;
 269         skb->nh.iph->daddr = cp->daddr;
 270         ip_send_check(skb->nh.iph);
 271
 272         IP_VS_DBG_PKT(10, pp, skb, 0, "After DNAT");
 273
 274         /* FIXME: when application helper enlarges the packet and the length
 275            is larger than the MTU of outgoing device, there will be still
 276            MTU problem. */
 277
 278         /* Another hack: avoid icmp_send in ip_fragment */
 279         skb->local_df = 1;
 280
 281         IP_VS_XMIT(skb, rt);
 282
 283         LeaveFunction(10);
 284         return NF_STOLEN;
 285
 286   tx_error_icmp:
 287         dst_link_failure(skb);
 288   tx_error:
 289         LeaveFunction(10);
 290         kfree_skb(skb);
 291         return NF_STOLEN;
 292   tx_error_put:
 293         ip_rt_put(rt);
 294         goto tx_error;
 295 }
 296
 297
 298 /*
 299  *   IP Tunneling transmitter
 300  *
 301  *   This function encapsulates the packet in a new IP packet, its
 302  *   destination will be set to cp->daddr. Most code of this function
 303  *   is taken from ipip.c.
 304  *
 305  *   It is used in VS/TUN cluster. The load balancer selects a real
 306  *   server from a cluster based on a scheduling algorithm,
 307  *   encapsulates the request packet and forwards it to the selected
 308  *   server. For example, all real servers are configured with
 309  *   "ifconfig tunl0 <Virtual IP Address> up". When the server receives
 310  *   the encapsulated packet, it will decapsulate the packet, processe
 311  *   the request and return the response packets directly to the client
 312  *   without passing the load balancer. This can greatly increase the
 313  *   scalability of virtual server.
 314  *
 315  *   Used for ANY protocol
 316  */
 317 int
 318 ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 319                   struct ip_vs_protocol *pp)
 320 {
 321         struct rtable *rt;                      /* Route to the other host */
 322         struct net_device *tdev;                /* Device to other host */
 323         struct iphdr  *old_iph = skb->nh.iph;
 324         u8     tos = old_iph->tos;
 325         u16    df = old_iph->frag_off;
 326         struct iphdr  *iph;                     /* Our new IP header */
 327         int    max_headroom;                    /* The extra header space needed */
 328         int    mtu;
 329
 330         EnterFunction(10);
 331
 332         if (skb->protocol != __constant_htons(ETH_P_IP)) {
 333                 IP_VS_DBG_RL("ip_vs_tunnel_xmit(): protocol error, "
 334                              "ETH_P_IP: %d, skb protocol: %d\n",
 335                              __constant_htons(ETH_P_IP), skb->protocol);
 336                 goto tx_error;
 337         }
 338
 339         if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(tos))))
 340                 goto tx_error_icmp;
 341
 342         tdev = rt->u.dst.dev;
 343
 344         mtu = dst_mtu(&rt->u.dst) - sizeof(struct iphdr);
 345         if (mtu < 68) {
 346                 ip_rt_put(rt);
 347                 IP_VS_DBG_RL("ip_vs_tunnel_xmit(): mtu less than 68\n");
 348                 goto tx_error;
 349         }
 350         if (skb->dst)
 351                 skb->dst->ops->update_pmtu(skb->dst, mtu);
 352
 353         df |= (old_iph->frag_off&__constant_htons(IP_DF));
 354
 355         if ((old_iph->frag_off&__constant_htons(IP_DF))
 356             && mtu < ntohs(old_iph->tot_len)) {
 357                 icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
 358                 ip_rt_put(rt);
 359                 IP_VS_DBG_RL("ip_vs_tunnel_xmit(): frag needed\n");
 360                 goto tx_error;
 361         }
 362
 363         /*
 364          * Okay, now see if we can stuff it in the buffer as-is.
 365          */
 366         max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr);
 367
 368         if (skb_headroom(skb) < max_headroom
 369             || skb_cloned(skb) || skb_shared(skb)) {
 370                 struct sk_buff *new_skb =
 371                         skb_realloc_headroom(skb, max_headroom);
 372                 if (!new_skb) {
 373                         ip_rt_put(rt);
 374                         kfree_skb(skb);
 375                         IP_VS_ERR_RL("ip_vs_tunnel_xmit(): no memory\n");
 376                         return NF_STOLEN;
 377                 }
 378                 kfree_skb(skb);
 379                 skb = new_skb;
 380                 old_iph = skb->nh.iph;
 381         }
 382
 383         skb->h.raw = (void *) old_iph;
 384
 385         /* fix old IP header checksum */
 386         ip_send_check(old_iph);
 387
 388         skb->nh.raw = skb_push(skb, sizeof(struct iphdr));
 389         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 390
 391         /* drop old route */
 392         dst_release(skb->dst);
 393         skb->dst = &rt->u.dst;
 394
 395         /*
 396          *      Push down and install the IPIP header.
 397          */
 398         iph                     =       skb->nh.iph;
 399         iph->version            =       4;
 400         iph->ihl                =       sizeof(struct iphdr)>>2;
 401         iph->frag_off           =       df;
 402         iph->protocol           =       IPPROTO_IPIP;
 403         iph->tos                =       tos;
 404         iph->daddr              =       rt->rt_dst;
 405         iph->saddr              =       rt->rt_src;
 406         iph->ttl                =       old_iph->ttl;
 407         iph->tot_len            =       htons(skb->len);
 408         ip_select_ident(iph, &rt->u.dst, NULL);
 409         ip_send_check(iph);
 410
 411         /* Another hack: avoid icmp_send in ip_fragment */
 412         skb->local_df = 1;
 413
 414         IP_VS_XMIT(skb, rt);
 415
 416         LeaveFunction(10);
 417
 418         return NF_STOLEN;
 419
 420   tx_error_icmp:
 421         dst_link_failure(skb);
 422   tx_error:
 423         kfree_skb(skb);
 424         LeaveFunction(10);
 425         return NF_STOLEN;
 426 }
 427
 428
 429 /*
 430  *      Direct Routing transmitter
 431  *      Used for ANY protocol
 432  */
 433 int
 434 ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 435               struct ip_vs_protocol *pp)
 436 {
 437         struct rtable *rt;                      /* Route to the other host */
 438         struct iphdr  *iph = skb->nh.iph;
 439         int    mtu;
 440
 441         EnterFunction(10);
 442
 443         if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
 444                 goto tx_error_icmp;
 445
 446         /* MTU checking */
 447         mtu = dst_mtu(&rt->u.dst);
 448         if ((iph->frag_off&__constant_htons(IP_DF)) && skb->len > mtu) {
 449                 icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
 450                 ip_rt_put(rt);
 451                 IP_VS_DBG_RL("ip_vs_dr_xmit(): frag needed\n");
 452                 goto tx_error;
 453         }
 454
 455         /*
 456          * Call ip_send_check because we are not sure it is called
 457          * after ip_defrag. Is copy-on-write needed?
 458          */
 459         if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
 460                 ip_rt_put(rt);
 461                 return NF_STOLEN;
 462         }
 463         ip_send_check(skb->nh.iph);
 464
 465         /* drop old route */
 466         dst_release(skb->dst);
 467         skb->dst = &rt->u.dst;
 468
 469         /* Another hack: avoid icmp_send in ip_fragment */
 470         skb->local_df = 1;
 471
 472         IP_VS_XMIT(skb, rt);
 473
 474         LeaveFunction(10);
 475         return NF_STOLEN;
 476
 477   tx_error_icmp:
 478         dst_link_failure(skb);
 479   tx_error:
 480         kfree_skb(skb);
 481         LeaveFunction(10);
 482         return NF_STOLEN;
 483 }
 484
 485
 486 /*
 487  *      ICMP packet transmitter
 488  *      called by the ip_vs_in_icmp
 489  */
 490 int
 491 ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 492                 struct ip_vs_protocol *pp, int offset)
 493 {
 494         struct rtable   *rt;    /* Route to the other host */
 495         int mtu;
 496         int rc;
 497
 498         EnterFunction(10);
 499
 500         /* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
 501            forwarded directly here, because there is no need to
 502            translate address/port back */
 503         if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
 504                 if (cp->packet_xmit)
 505                         rc = cp->packet_xmit(skb, cp, pp);
 506                 else
 507                         rc = NF_ACCEPT;
 508                 /* do not touch skb anymore */
 509                 atomic_inc(&cp->in_pkts);
 510                 goto out;
 511         }
 512
 513         /*
 514          * mangle and send the packet here (only for VS/NAT)
 515          */
 516
 517         if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(skb->nh.iph->tos))))
 518                 goto tx_error_icmp;
 519
 520         /* MTU checking */
 521         mtu = dst_mtu(&rt->u.dst);
 522         if ((skb->len > mtu) && (skb->nh.iph->frag_off&__constant_htons(IP_DF))) {
 523                 ip_rt_put(rt);
 524                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
 525                 IP_VS_DBG_RL("ip_vs_in_icmp(): frag needed\n");
 526                 goto tx_error;
 527         }
 528
 529         /* copy-on-write the packet before mangling it */
 530         if (!ip_vs_make_skb_writable(&skb, offset))
 531                 goto tx_error_put;
 532
 533         if (skb_cow(skb, rt->u.dst.dev->hard_header_len))
 534                 goto tx_error_put;
 535
 536         /* drop the old route when skb is not shared */
 537         dst_release(skb->dst);
 538         skb->dst = &rt->u.dst;
 539
 540         ip_vs_nat_icmp(skb, pp, cp, 0);
 541
 542         /* Another hack: avoid icmp_send in ip_fragment */
 543         skb->local_df = 1;
 544
 545         IP_VS_XMIT(skb, rt);
 546
 547         rc = NF_STOLEN;
 548         goto out;
 549
 550   tx_error_icmp:
 551         dst_link_failure(skb);
 552   tx_error:
 553         dev_kfree_skb(skb);
 554         rc = NF_STOLEN;
 555   out:
 556         LeaveFunction(10);
 557         return rc;
 558   tx_error_put:
 559         ip_rt_put(rt);
 560         goto tx_error;
 561 }