net/ipv4/ipvs/ip_vs_xmit.c

   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         nf_reset_debug(skb);                            \
 131         (skb)->nfcache |= NFC_IPVS_PROPERTY;            \
 132         (skb)->ip_summed = CHECKSUM_NONE;               \
 133         NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, (skb), NULL,  \
 134                 (rt)->u.dst.dev, dst_output);           \
 135 } while (0)
 136
 137
 138 /*
 139  *      NULL transmitter (do nothing except return NF_ACCEPT)
 140  */
 141 int
 142 ip_vs_null_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 143                 struct ip_vs_protocol *pp)
 144 {
 145         /* we do not touch skb and do not need pskb ptr */
 146         return NF_ACCEPT;
 147 }
 148
 149
 150 /*
 151  *      Bypass transmitter
 152  *      Let packets bypass the destination when the destination is not
 153  *      available, it may be only used in transparent cache cluster.
 154  */
 155 int
 156 ip_vs_bypass_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 157                   struct ip_vs_protocol *pp)
 158 {
 159         struct rtable *rt;                      /* Route to the other host */
 160         struct iphdr  *iph = skb->nh.iph;
 161         u8     tos = iph->tos;
 162         int    mtu;
 163         struct flowi fl = {
 164                 .oif = 0,
 165                 .nl_u = {
 166                         .ip4_u = {
 167                                 .daddr = iph->daddr,
 168                                 .saddr = 0,
 169                                 .tos = RT_TOS(tos), } },
 170         };
 171
 172         EnterFunction(10);
 173
 174         if (ip_route_output_key(&rt, &fl)) {
 175                 IP_VS_DBG_RL("ip_vs_bypass_xmit(): ip_route_output error, "
 176                              "dest: %u.%u.%u.%u\n", NIPQUAD(iph->daddr));
 177                 goto tx_error_icmp;
 178         }
 179
 180         /* MTU checking */
 181         mtu = dst_mtu(&rt->u.dst);
 182         if ((skb->len > mtu) && (iph->frag_off&__constant_htons(IP_DF))) {
 183                 ip_rt_put(rt);
 184                 icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
 185                 IP_VS_DBG_RL("ip_vs_bypass_xmit(): frag needed\n");
 186                 goto tx_error;
 187         }
 188
 189         /*
 190          * Call ip_send_check because we are not sure it is called
 191          * after ip_defrag. Is copy-on-write needed?
 192          */
 193         if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
 194                 ip_rt_put(rt);
 195                 return NF_STOLEN;
 196         }
 197         ip_send_check(skb->nh.iph);
 198
 199         /* drop old route */
 200         dst_release(skb->dst);
 201         skb->dst = &rt->u.dst;
 202
 203         /* Another hack: avoid icmp_send in ip_fragment */
 204         skb->local_df = 1;
 205
 206         IP_VS_XMIT(skb, rt);
 207
 208         LeaveFunction(10);
 209         return NF_STOLEN;
 210
 211  tx_error_icmp:
 212         dst_link_failure(skb);
 213  tx_error:
 214         kfree_skb(skb);
 215         LeaveFunction(10);
 216         return NF_STOLEN;
 217 }
 218
 219
 220 /*
 221  *      NAT transmitter (only for outside-to-inside nat forwarding)
 222  *      Not used for related ICMP
 223  */
 224 int
 225 ip_vs_nat_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 226                struct ip_vs_protocol *pp)
 227 {
 228         struct rtable *rt;              /* Route to the other host */
 229         int mtu;
 230         struct iphdr *iph = skb->nh.iph;
 231
 232         EnterFunction(10);
 233
 234         /* check if it is a connection of no-client-port */
 235         if (unlikely(cp->flags & IP_VS_CONN_F_NO_CPORT)) {
 236                 __u16 _pt, *p;
 237                 p = skb_header_pointer(skb, iph->ihl*4, sizeof(_pt), &_pt);
 238                 if (p == NULL)
 239                         goto tx_error;
 240                 ip_vs_conn_fill_cport(cp, *p);
 241                 IP_VS_DBG(10, "filled cport=%d\n", ntohs(*p));
 242         }
 243
 244         if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
 245                 goto tx_error_icmp;
 246
 247         /* MTU checking */
 248         mtu = dst_mtu(&rt->u.dst);
 249         if ((skb->len > mtu) && (iph->frag_off&__constant_htons(IP_DF))) {
 250                 ip_rt_put(rt);
 251                 icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
 252                 IP_VS_DBG_RL_PKT(0, pp, skb, 0, "ip_vs_nat_xmit(): frag needed for");
 253                 goto tx_error;
 254         }
 255
 256         /* copy-on-write the packet before mangling it */
 257         if (!ip_vs_make_skb_writable(&skb, sizeof(struct iphdr)))
 258                 goto tx_error_put;
 259
 260         if (skb_cow(skb, rt->u.dst.dev->hard_header_len))
 261                 goto tx_error_put;
 262
 263         /* drop old route */
 264         dst_release(skb->dst);
 265         skb->dst = &rt->u.dst;
 266
 267         /* mangle the packet */
 268         if (pp->dnat_handler && !pp->dnat_handler(&skb, pp, cp))
 269                 goto tx_error;
 270         skb->nh.iph->daddr = cp->daddr;
 271         ip_send_check(skb->nh.iph);
 272
 273         IP_VS_DBG_PKT(10, pp, skb, 0, "After DNAT");
 274
 275         /* FIXME: when application helper enlarges the packet and the length
 276            is larger than the MTU of outgoing device, there will be still
 277            MTU problem. */
 278
 279         /* Another hack: avoid icmp_send in ip_fragment */
 280         skb->local_df = 1;
 281
 282         IP_VS_XMIT(skb, rt);
 283
 284         LeaveFunction(10);
 285         return NF_STOLEN;
 286
 287   tx_error_icmp:
 288         dst_link_failure(skb);
 289   tx_error:
 290         LeaveFunction(10);
 291         kfree_skb(skb);
 292         return NF_STOLEN;
 293   tx_error_put:
 294         ip_rt_put(rt);
 295         goto tx_error;
 296 }
 297
 298
 299 /*
 300  *   IP Tunneling transmitter
 301  *
 302  *   This function encapsulates the packet in a new IP packet, its
 303  *   destination will be set to cp->daddr. Most code of this function
 304  *   is taken from ipip.c.
 305  *
 306  *   It is used in VS/TUN cluster. The load balancer selects a real
 307  *   server from a cluster based on a scheduling algorithm,
 308  *   encapsulates the request packet and forwards it to the selected
 309  *   server. For example, all real servers are configured with
 310  *   "ifconfig tunl0 <Virtual IP Address> up". When the server receives
 311  *   the encapsulated packet, it will decapsulate the packet, processe
 312  *   the request and return the response packets directly to the client
 313  *   without passing the load balancer. This can greatly increase the
 314  *   scalability of virtual server.
 315  *
 316  *   Used for ANY protocol
 317  */
 318 int
 319 ip_vs_tunnel_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 320                   struct ip_vs_protocol *pp)
 321 {
 322         struct rtable *rt;                      /* Route to the other host */
 323         struct net_device *tdev;                /* Device to other host */
 324         struct iphdr  *old_iph = skb->nh.iph;
 325         u8     tos = old_iph->tos;
 326         u16    df = old_iph->frag_off;
 327         struct iphdr  *iph;                     /* Our new IP header */
 328         int    max_headroom;                    /* The extra header space needed */
 329         int    mtu;
 330
 331         EnterFunction(10);
 332
 333         if (skb->protocol != __constant_htons(ETH_P_IP)) {
 334                 IP_VS_DBG_RL("ip_vs_tunnel_xmit(): protocol error, "
 335                              "ETH_P_IP: %d, skb protocol: %d\n",
 336                              __constant_htons(ETH_P_IP), skb->protocol);
 337                 goto tx_error;
 338         }
 339
 340         if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(tos))))
 341                 goto tx_error_icmp;
 342
 343         tdev = rt->u.dst.dev;
 344
 345         mtu = dst_mtu(&rt->u.dst) - sizeof(struct iphdr);
 346         if (mtu < 68) {
 347                 ip_rt_put(rt);
 348                 IP_VS_DBG_RL("ip_vs_tunnel_xmit(): mtu less than 68\n");
 349                 goto tx_error;
 350         }
 351         if (skb->dst)
 352                 skb->dst->ops->update_pmtu(skb->dst, mtu);
 353
 354         df |= (old_iph->frag_off&__constant_htons(IP_DF));
 355
 356         if ((old_iph->frag_off&__constant_htons(IP_DF))
 357             && mtu < ntohs(old_iph->tot_len)) {
 358                 icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
 359                 ip_rt_put(rt);
 360                 IP_VS_DBG_RL("ip_vs_tunnel_xmit(): frag needed\n");
 361                 goto tx_error;
 362         }
 363
 364         /*
 365          * Okay, now see if we can stuff it in the buffer as-is.
 366          */
 367         max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(struct iphdr);
 368
 369         if (skb_headroom(skb) < max_headroom
 370             || skb_cloned(skb) || skb_shared(skb)) {
 371                 struct sk_buff *new_skb =
 372                         skb_realloc_headroom(skb, max_headroom);
 373                 if (!new_skb) {
 374                         ip_rt_put(rt);
 375                         kfree_skb(skb);
 376                         IP_VS_ERR_RL("ip_vs_tunnel_xmit(): no memory\n");
 377                         return NF_STOLEN;
 378                 }
 379                 kfree_skb(skb);
 380                 skb = new_skb;
 381                 old_iph = skb->nh.iph;
 382         }
 383
 384         skb->h.raw = (void *) old_iph;
 385
 386         /* fix old IP header checksum */
 387         ip_send_check(old_iph);
 388
 389         skb->nh.raw = skb_push(skb, sizeof(struct iphdr));
 390         memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 391
 392         /* drop old route */
 393         dst_release(skb->dst);
 394         skb->dst = &rt->u.dst;
 395
 396         /*
 397          *      Push down and install the IPIP header.
 398          */
 399         iph                     =       skb->nh.iph;
 400         iph->version            =       4;
 401         iph->ihl                =       sizeof(struct iphdr)>>2;
 402         iph->frag_off           =       df;
 403         iph->protocol           =       IPPROTO_IPIP;
 404         iph->tos                =       tos;
 405         iph->daddr              =       rt->rt_dst;
 406         iph->saddr              =       rt->rt_src;
 407         iph->ttl                =       old_iph->ttl;
 408         iph->tot_len            =       htons(skb->len);
 409         ip_select_ident(iph, &rt->u.dst, NULL);
 410         ip_send_check(iph);
 411
 412         /* Another hack: avoid icmp_send in ip_fragment */
 413         skb->local_df = 1;
 414
 415         IP_VS_XMIT(skb, rt);
 416
 417         LeaveFunction(10);
 418
 419         return NF_STOLEN;
 420
 421   tx_error_icmp:
 422         dst_link_failure(skb);
 423   tx_error:
 424         kfree_skb(skb);
 425         LeaveFunction(10);
 426         return NF_STOLEN;
 427 }
 428
 429
 430 /*
 431  *      Direct Routing transmitter
 432  *      Used for ANY protocol
 433  */
 434 int
 435 ip_vs_dr_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 436               struct ip_vs_protocol *pp)
 437 {
 438         struct rtable *rt;                      /* Route to the other host */
 439         struct iphdr  *iph = skb->nh.iph;
 440         int    mtu;
 441
 442         EnterFunction(10);
 443
 444         if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
 445                 goto tx_error_icmp;
 446
 447         /* MTU checking */
 448         mtu = dst_mtu(&rt->u.dst);
 449         if ((iph->frag_off&__constant_htons(IP_DF)) && skb->len > mtu) {
 450                 icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
 451                 ip_rt_put(rt);
 452                 IP_VS_DBG_RL("ip_vs_dr_xmit(): frag needed\n");
 453                 goto tx_error;
 454         }
 455
 456         /*
 457          * Call ip_send_check because we are not sure it is called
 458          * after ip_defrag. Is copy-on-write needed?
 459          */
 460         if (unlikely((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)) {
 461                 ip_rt_put(rt);
 462                 return NF_STOLEN;
 463         }
 464         ip_send_check(skb->nh.iph);
 465
 466         /* drop old route */
 467         dst_release(skb->dst);
 468         skb->dst = &rt->u.dst;
 469
 470         /* Another hack: avoid icmp_send in ip_fragment */
 471         skb->local_df = 1;
 472
 473         IP_VS_XMIT(skb, rt);
 474
 475         LeaveFunction(10);
 476         return NF_STOLEN;
 477
 478   tx_error_icmp:
 479         dst_link_failure(skb);
 480   tx_error:
 481         kfree_skb(skb);
 482         LeaveFunction(10);
 483         return NF_STOLEN;
 484 }
 485
 486
 487 /*
 488  *      ICMP packet transmitter
 489  *      called by the ip_vs_in_icmp
 490  */
 491 int
 492 ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
 493                 struct ip_vs_protocol *pp, int offset)
 494 {
 495         struct rtable   *rt;    /* Route to the other host */
 496         int mtu;
 497         int rc;
 498
 499         EnterFunction(10);
 500
 501         /* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
 502            forwarded directly here, because there is no need to
 503            translate address/port back */
 504         if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
 505                 if (cp->packet_xmit)
 506                         rc = cp->packet_xmit(skb, cp, pp);
 507                 else
 508                         rc = NF_ACCEPT;
 509                 /* do not touch skb anymore */
 510                 atomic_inc(&cp->in_pkts);
 511                 goto out;
 512         }
 513
 514         /*
 515          * mangle and send the packet here (only for VS/NAT)
 516          */
 517
 518         if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(skb->nh.iph->tos))))
 519                 goto tx_error_icmp;
 520
 521         /* MTU checking */
 522         mtu = dst_mtu(&rt->u.dst);
 523         if ((skb->len > mtu) && (skb->nh.iph->frag_off&__constant_htons(IP_DF))) {
 524                 ip_rt_put(rt);
 525                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
 526                 IP_VS_DBG_RL("ip_vs_in_icmp(): frag needed\n");
 527                 goto tx_error;
 528         }
 529
 530         /* copy-on-write the packet before mangling it */
 531         if (!ip_vs_make_skb_writable(&skb, offset))
 532                 goto tx_error_put;
 533
 534         if (skb_cow(skb, rt->u.dst.dev->hard_header_len))
 535                 goto tx_error_put;
 536
 537         /* drop the old route when skb is not shared */
 538         dst_release(skb->dst);
 539         skb->dst = &rt->u.dst;
 540
 541         ip_vs_nat_icmp(skb, pp, cp, 0);
 542
 543         /* Another hack: avoid icmp_send in ip_fragment */
 544         skb->local_df = 1;
 545
 546         IP_VS_XMIT(skb, rt);
 547
 548         rc = NF_STOLEN;
 549         goto out;
 550
 551   tx_error_icmp:
 552         dst_link_failure(skb);
 553   tx_error:
 554         dev_kfree_skb(skb);
 555         rc = NF_STOLEN;
 556   out:
 557         LeaveFunction(10);
 558         return rc;
 559   tx_error_put:
 560         ip_rt_put(rt);
 561         goto tx_error;
 562 }