1 /*-
2 * Copyright (c) 2016-2020 Netflix, Inc.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
16 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
23 * SUCH DAMAGE.
24 *
25 */
26 /*
27 * Author: Randall Stewart <rrs@netflix.com>
28 * This work is based on the ACM Queue paper
29 * BBR - Congestion Based Congestion Control
30 * and also numerous discussions with Neal, Yuchung and Van.
31 */
32
33 #include <sys/cdefs.h>
34 #include "opt_inet.h"
35 #include "opt_inet6.h"
36 #include "opt_ipsec.h"
37 #include "opt_ratelimit.h"
38 #include <sys/param.h>
39 #include <sys/arb.h>
40 #include <sys/module.h>
41 #include <sys/kernel.h>
42 #ifdef TCP_HHOOK
43 #include <sys/hhook.h>
44 #endif
45 #include <sys/malloc.h>
46 #include <sys/mbuf.h>
47 #include <sys/proc.h>
48 #include <sys/qmath.h>
49 #include <sys/socket.h>
50 #include <sys/socketvar.h>
51 #include <sys/sysctl.h>
52 #include <sys/systm.h>
53 #include <sys/tree.h>
54 #ifdef NETFLIX_STATS
55 #include <sys/stats.h> /* Must come after qmath.h and tree.h */
56 #endif
57 #include <sys/refcount.h>
58 #include <sys/queue.h>
59 #include <sys/smp.h>
60 #include <sys/kthread.h>
61 #include <sys/lock.h>
62 #include <sys/mutex.h>
63 #include <sys/tim_filter.h>
64 #include <sys/time.h>
65 #include <vm/uma.h>
66 #include <sys/kern_prefetch.h>
67
68 #include <net/route.h>
69 #include <net/vnet.h>
70 #include <net/ethernet.h>
71 #include <net/bpf.h>
72
73 #define TCPSTATES /* for logging */
74
75 #include <netinet/in.h>
76 #include <netinet/in_kdtrace.h>
77 #include <netinet/in_pcb.h>
78 #include <netinet/ip.h>
79 #include <netinet/ip_icmp.h> /* required for icmp_var.h */
80 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
81 #include <netinet/ip_var.h>
82 #include <netinet/ip6.h>
83 #include <netinet6/in6_pcb.h>
84 #include <netinet6/ip6_var.h>
85 #include <netinet/tcp.h>
86 #include <netinet/tcp_fsm.h>
87 #include <netinet/tcp_seq.h>
88 #include <netinet/tcp_timer.h>
89 #include <netinet/tcp_var.h>
90 #include <netinet/tcpip.h>
91 #include <netinet/tcp_ecn.h>
92 #include <netinet/tcp_hpts.h>
93 #include <netinet/tcp_lro.h>
94 #include <netinet/cc/cc.h>
95 #include <netinet/tcp_log_buf.h>
96 #ifdef TCP_OFFLOAD
97 #include <netinet/tcp_offload.h>
98 #endif
99 #ifdef INET6
100 #include <netinet6/tcp6_var.h>
101 #endif
102 #include <netinet/tcp_fastopen.h>
103
104 #include <netipsec/ipsec_support.h>
105 #include <net/if.h>
106 #include <net/if_var.h>
107 #include <net/if_private.h>
108
109 #if defined(IPSEC) || defined(IPSEC_SUPPORT)
110 #include <netipsec/ipsec.h>
111 #include <netipsec/ipsec6.h>
112 #endif /* IPSEC */
113
114 #include <netinet/udp.h>
115 #include <netinet/udp_var.h>
116 #include <machine/in_cksum.h>
117
118 #ifdef MAC
119 #include <security/mac/mac_framework.h>
120 #endif
121 #include "rack_bbr_common.h"
122
123 /*
124 * Common TCP Functions - These are shared by borth
125 * rack and BBR.
126 */
127 static int
ctf_get_enet_type(struct ifnet * ifp,struct mbuf * m)128 ctf_get_enet_type(struct ifnet *ifp, struct mbuf *m)
129 {
130 struct ether_header *eh;
131 #ifdef INET6
132 struct ip6_hdr *ip6 = NULL; /* Keep compiler happy. */
133 #endif
134 #ifdef INET
135 struct ip *ip = NULL; /* Keep compiler happy. */
136 #endif
137 #if defined(INET) || defined(INET6)
138 struct tcphdr *th;
139 int32_t tlen;
140 uint16_t drop_hdrlen;
141 #endif
142 uint16_t etype;
143 #ifdef INET
144 uint8_t iptos;
145 #endif
146
147 /* Is it the easy way? */
148 if (m->m_flags & M_LRO_EHDRSTRP)
149 return (m->m_pkthdr.lro_etype);
150 /*
151 * Ok this is the old style call, the ethernet header is here.
152 * This also means no checksum or BPF were done. This
153 * can happen if the race to setup the inp fails and
154 * LRO sees no INP at packet input, but by the time
155 * we queue the packets an INP gets there. Its rare
156 * but it can occur so we will handle it. Note that
157 * this means duplicated work but with the rarity of it
158 * its not worth worrying about.
159 */
160 /* Let the BPF see the packet */
161 if (bpf_peers_present(ifp->if_bpf))
162 ETHER_BPF_MTAP(ifp, m);
163 /* Now the csum */
164 eh = mtod(m, struct ether_header *);
165 etype = ntohs(eh->ether_type);
166 m_adj(m, sizeof(*eh));
167 switch (etype) {
168 #ifdef INET6
169 case ETHERTYPE_IPV6:
170 {
171 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
172 m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
173 if (m == NULL) {
174 KMOD_TCPSTAT_INC(tcps_rcvshort);
175 return (-1);
176 }
177 }
178 ip6 = (struct ip6_hdr *)(eh + 1);
179 th = (struct tcphdr *)(ip6 + 1);
180 drop_hdrlen = sizeof(*ip6);
181 tlen = ntohs(ip6->ip6_plen);
182 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
183 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
184 th->th_sum = m->m_pkthdr.csum_data;
185 else
186 th->th_sum = in6_cksum_pseudo(ip6, tlen,
187 IPPROTO_TCP,
188 m->m_pkthdr.csum_data);
189 th->th_sum ^= 0xffff;
190 } else
191 th->th_sum = in6_cksum(m, IPPROTO_TCP, drop_hdrlen, tlen);
192 if (th->th_sum) {
193 KMOD_TCPSTAT_INC(tcps_rcvbadsum);
194 m_freem(m);
195 return (-1);
196 }
197 return (etype);
198 }
199 #endif
200 #ifdef INET
201 case ETHERTYPE_IP:
202 {
203 if (m->m_len < sizeof (struct tcpiphdr)) {
204 m = m_pullup(m, sizeof (struct tcpiphdr));
205 if (m == NULL) {
206 KMOD_TCPSTAT_INC(tcps_rcvshort);
207 return (-1);
208 }
209 }
210 ip = (struct ip *)(eh + 1);
211 th = (struct tcphdr *)(ip + 1);
212 drop_hdrlen = sizeof(*ip);
213 iptos = ip->ip_tos;
214 tlen = ntohs(ip->ip_len) - sizeof(struct ip);
215 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
216 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
217 th->th_sum = m->m_pkthdr.csum_data;
218 else
219 th->th_sum = in_pseudo(ip->ip_src.s_addr,
220 ip->ip_dst.s_addr,
221 htonl(m->m_pkthdr.csum_data + tlen + IPPROTO_TCP));
222 th->th_sum ^= 0xffff;
223 } else {
224 int len;
225 struct ipovly *ipov = (struct ipovly *)ip;
226 /*
227 * Checksum extended TCP header and data.
228 */
229 len = drop_hdrlen + tlen;
230 bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
231 ipov->ih_len = htons(tlen);
232 th->th_sum = in_cksum(m, len);
233 /* Reset length for SDT probes. */
234 ip->ip_len = htons(len);
235 /* Reset TOS bits */
236 ip->ip_tos = iptos;
237 /* Re-initialization for later version check */
238 ip->ip_v = IPVERSION;
239 ip->ip_hl = sizeof(*ip) >> 2;
240 }
241 if (th->th_sum) {
242 KMOD_TCPSTAT_INC(tcps_rcvbadsum);
243 m_freem(m);
244 return (-1);
245 }
246 break;
247 }
248 #endif
249 };
250 return (etype);
251 }
252
253 /*
254 * The function ctf_process_inbound_raw() is used by
255 * transport developers to do the steps needed to
256 * support MBUF Queuing i.e. the flags in
257 * inp->inp_flags2:
258 *
259 * - INP_SUPPORTS_MBUFQ
260 * - INP_MBUF_QUEUE_READY
261 * - INP_DONT_SACK_QUEUE
262 * - INP_MBUF_ACKCMP
263 *
264 * These flags help control how LRO will deliver
265 * packets to the transport. You first set in inp_flags2
266 * the INP_SUPPORTS_MBUFQ to tell the LRO code that you
267 * will gladly take a queue of packets instead of a compressed
268 * single packet. You also set in your t_fb pointer the
269 * tfb_do_queued_segments to point to ctf_process_inbound_raw.
270 *
271 * This then gets you lists of inbound ACK's/Data instead
272 * of a condensed compressed ACK/DATA packet. Why would you
273 * want that? This will get you access to all the arrival
274 * times of at least LRO and possibly at the Hardware (if
275 * the interface card supports that) of the actual ACK/DATA.
276 * In some transport designs this is important since knowing
277 * the actual time we got the packet is useful information.
278 *
279 * A new special type of mbuf may also be supported by the transport
280 * if it has set the INP_MBUF_ACKCMP flag. If its set, LRO will
281 * possibly create a M_ACKCMP type mbuf. This is a mbuf with
282 * an array of "acks". One thing also to note is that when this
283 * occurs a subsequent LRO may find at the back of the untouched
284 * mbuf queue chain a M_ACKCMP and append on to it. This means
285 * that until the transport pulls in the mbuf chain queued
286 * for it more ack's may get on the mbufs that were already
287 * delivered. There currently is a limit of 6 acks condensed
288 * into 1 mbuf which means often when this is occuring, we
289 * don't get that effect but it does happen.
290 *
291 * Now there are some interesting Caveats that the transport
292 * designer needs to take into account when using this feature.
293 *
294 * 1) It is used with HPTS and pacing, when the pacing timer
295 * for output calls it will first call the input.
296 * 2) When you set INP_MBUF_QUEUE_READY this tells LRO
297 * queue normal packets, I am busy pacing out data and
298 * will process the queued packets before my tfb_tcp_output
299 * call from pacing. If a non-normal packet arrives, (e.g. sack)
300 * you will be awoken immediately.
301 * 3) Finally you can add the INP_DONT_SACK_QUEUE to not even
302 * be awoken if a SACK has arrived. You would do this when
303 * you were not only running a pacing for output timer
304 * but a Rack timer as well i.e. you know you are in recovery
305 * and are in the process (via the timers) of dealing with
306 * the loss.
307 *
308 * Now a critical thing you must be aware of here is that the
309 * use of the flags has a far greater scope then just your
310 * typical LRO. Why? Well thats because in the normal compressed
311 * LRO case at the end of a driver interupt all packets are going
312 * to get presented to the transport no matter if there is one
313 * or 100. With the MBUF_QUEUE model, this is not true. You will
314 * only be awoken to process the queue of packets when:
315 * a) The flags discussed above allow it.
316 * <or>
317 * b) You exceed a ack or data limit (by default the
318 * ack limit is infinity (64k acks) and the data
319 * limit is 64k of new TCP data)
320 * <or>
321 * c) The push bit has been set by the peer
322 */
323
324 static int
ctf_process_inbound_raw(struct tcpcb * tp,struct mbuf * m,int has_pkt)325 ctf_process_inbound_raw(struct tcpcb *tp, struct mbuf *m, int has_pkt)
326 {
327 /*
328 * We are passed a raw change of mbuf packets
329 * that arrived in LRO. They are linked via
330 * the m_nextpkt link in the pkt-headers.
331 *
332 * We process each one by:
333 * a) saving off the next
334 * b) stripping off the ether-header
335 * c) formulating the arguments for tfb_do_segment_nounlock()
336 * d) calling each mbuf to tfb_do_segment_nounlock()
337 * after adjusting the time to match the arrival time.
338 * Note that the LRO code assures no IP options are present.
339 *
340 * The symantics for calling tfb_do_segment_nounlock() are the
341 * following:
342 * 1) It returns 0 if all went well and you (the caller) need
343 * to release the lock.
344 * 2) If nxt_pkt is set, then the function will surpress calls
345 * to tcp_output() since you are promising to call again
346 * with another packet.
347 * 3) If it returns 1, then you must free all the packets being
348 * shipped in, the tcb has been destroyed (or about to be destroyed).
349 */
350 struct mbuf *m_save;
351 struct tcphdr *th;
352 #ifdef INET6
353 struct ip6_hdr *ip6 = NULL; /* Keep compiler happy. */
354 #endif
355 #ifdef INET
356 struct ip *ip = NULL; /* Keep compiler happy. */
357 #endif
358 struct ifnet *ifp;
359 struct timeval tv;
360 struct inpcb *inp __diagused;
361 int32_t retval, nxt_pkt, tlen, off;
362 int etype = 0;
363 uint16_t drop_hdrlen;
364 uint8_t iptos;
365
366 inp = tptoinpcb(tp);
367 INP_WLOCK_ASSERT(inp);
368 NET_EPOCH_ASSERT();
369 KASSERT(m != NULL, ("ctf_process_inbound_raw: m == NULL"));
370 ifp = m_rcvif(m);
371 KASSERT(ifp != NULL, ("ctf_process_inbound_raw: ifp == NULL"));
372 CURVNET_SET(ifp->if_vnet);
373 tcp_get_usecs(&tv);
374 while (m) {
375 m_save = m->m_nextpkt;
376 m->m_nextpkt = NULL;
377 if ((m->m_flags & M_ACKCMP) == 0) {
378 /* Now lets get the ether header */
379 etype = ctf_get_enet_type(ifp, m);
380 if (etype == -1) {
381 /* Skip this packet it was freed by checksum */
382 goto skipped_pkt;
383 }
384 KASSERT(((etype == ETHERTYPE_IPV6) || (etype == ETHERTYPE_IP)),
385 ("tp:%p m:%p etype:0x%x -- not IP or IPv6", tp, m, etype));
386 /* Trim off the ethernet header */
387 switch (etype) {
388 #ifdef INET6
389 case ETHERTYPE_IPV6:
390 ip6 = mtod(m, struct ip6_hdr *);
391 th = (struct tcphdr *)(ip6 + 1);
392 tlen = ntohs(ip6->ip6_plen);
393 drop_hdrlen = sizeof(*ip6);
394 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
395 break;
396 #endif
397 #ifdef INET
398 case ETHERTYPE_IP:
399 ip = mtod(m, struct ip *);
400 th = (struct tcphdr *)(ip + 1);
401 drop_hdrlen = sizeof(*ip);
402 iptos = ip->ip_tos;
403 tlen = ntohs(ip->ip_len) - sizeof(struct ip);
404 break;
405 #endif
406 } /* end switch */
407 off = th->th_off << 2;
408 if (off < sizeof (struct tcphdr) || off > tlen) {
409 printf("off:%d < hdrlen:%zu || > tlen:%u -- dump\n",
410 off,
411 sizeof(struct tcphdr),
412 tlen);
413 KMOD_TCPSTAT_INC(tcps_rcvbadoff);
414 m_freem(m);
415 goto skipped_pkt;
416 }
417 tlen -= off;
418 drop_hdrlen += off;
419 /*
420 * Now lets setup the timeval to be when we should
421 * have been called (if we can).
422 */
423 m->m_pkthdr.lro_nsegs = 1;
424 /* Now what about next packet? */
425 } else {
426 /*
427 * This mbuf is an array of acks that have
428 * been compressed. We assert the inp has
429 * the flag set to enable this!
430 */
431 KASSERT((tp->t_flags2 & TF2_MBUF_ACKCMP),
432 ("tp:%p no TF2_MBUF_ACKCMP flags?", tp));
433 tlen = 0;
434 drop_hdrlen = 0;
435 th = NULL;
436 iptos = 0;
437 }
438 tcp_get_usecs(&tv);
439 if (m_save || has_pkt)
440 nxt_pkt = 1;
441 else
442 nxt_pkt = 0;
443 if ((m->m_flags & M_ACKCMP) == 0)
444 KMOD_TCPSTAT_INC(tcps_rcvtotal);
445 else
446 KMOD_TCPSTAT_ADD(tcps_rcvtotal, (m->m_len / sizeof(struct tcp_ackent)));
447 retval = (*tp->t_fb->tfb_do_segment_nounlock)(tp, m, th,
448 drop_hdrlen, tlen, iptos, nxt_pkt, &tv);
449 if (retval) {
450 /* We lost the lock and tcb probably */
451 m = m_save;
452 while(m) {
453 m_save = m->m_nextpkt;
454 m->m_nextpkt = NULL;
455 m_freem(m);
456 m = m_save;
457 }
458 CURVNET_RESTORE();
459 INP_UNLOCK_ASSERT(inp);
460 return (retval);
461 }
462 skipped_pkt:
463 m = m_save;
464 }
465 CURVNET_RESTORE();
466 return (0);
467 }
468
469 int
ctf_do_queued_segments(struct tcpcb * tp,int have_pkt)470 ctf_do_queued_segments(struct tcpcb *tp, int have_pkt)
471 {
472 struct mbuf *m;
473
474 /* First lets see if we have old packets */
475 if ((m = STAILQ_FIRST(&tp->t_inqueue)) != NULL) {
476 STAILQ_INIT(&tp->t_inqueue);
477 if (ctf_process_inbound_raw(tp, m, have_pkt)) {
478 /* We lost the tcpcb (maybe a RST came in)? */
479 return(1);
480 }
481 }
482 return (0);
483 }
484
485 uint32_t
ctf_outstanding(struct tcpcb * tp)486 ctf_outstanding(struct tcpcb *tp)
487 {
488 uint32_t bytes_out;
489
490 bytes_out = tp->snd_max - tp->snd_una;
491 if (tp->t_state < TCPS_ESTABLISHED)
492 bytes_out++;
493 if (tp->t_flags & TF_SENTFIN)
494 bytes_out++;
495 return (bytes_out);
496 }
497
498 uint32_t
ctf_flight_size(struct tcpcb * tp,uint32_t rc_sacked)499 ctf_flight_size(struct tcpcb *tp, uint32_t rc_sacked)
500 {
501 if (rc_sacked <= ctf_outstanding(tp))
502 return(ctf_outstanding(tp) - rc_sacked);
503 else {
504 return (0);
505 }
506 }
507
508 void
ctf_do_dropwithreset(struct mbuf * m,struct tcpcb * tp,struct tcphdr * th,int32_t rstreason,int32_t tlen)509 ctf_do_dropwithreset(struct mbuf *m, struct tcpcb *tp, struct tcphdr *th,
510 int32_t rstreason, int32_t tlen)
511 {
512 if (tp != NULL) {
513 tcp_dropwithreset(m, th, tp, tlen, rstreason);
514 INP_WUNLOCK(tptoinpcb(tp));
515 } else
516 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
517 }
518
519 void
ctf_ack_war_checks(struct tcpcb * tp,uint32_t * ts,uint32_t * cnt)520 ctf_ack_war_checks(struct tcpcb *tp, uint32_t *ts, uint32_t *cnt)
521 {
522 if ((ts != NULL) && (cnt != NULL) &&
523 (V_tcp_ack_war_time_window > 0) &&
524 (V_tcp_ack_war_cnt > 0)) {
525 /* We are possibly doing ack war prevention */
526 uint32_t cts;
527
528 /*
529 * We use a msec tick here which gives us
530 * roughly 49 days. We don't need the
531 * precision of a microsecond timestamp which
532 * would only give us hours.
533 */
534 cts = tcp_ts_getticks();
535 if (TSTMP_LT((*ts), cts)) {
536 /* Timestamp is in the past */
537 *cnt = 0;
538 *ts = (cts + V_tcp_ack_war_time_window);
539 }
540 if (*cnt < V_tcp_ack_war_cnt) {
541 *cnt = (*cnt + 1);
542 tp->t_flags |= TF_ACKNOW;
543 } else
544 tp->t_flags &= ~TF_ACKNOW;
545 } else
546 tp->t_flags |= TF_ACKNOW;
547 }
548
549 /*
550 * ctf_drop_checks returns 1 for you should not proceed. It places
551 * in ret_val what should be returned 1/0 by the caller. The 1 indicates
552 * that the TCB is unlocked and probably dropped. The 0 indicates the
553 * TCB is still valid and locked.
554 */
555 int
_ctf_drop_checks(struct tcpopt * to,struct mbuf * m,struct tcphdr * th,struct tcpcb * tp,int32_t * tlenp,int32_t * thf,int32_t * drop_hdrlen,int32_t * ret_val,uint32_t * ts,uint32_t * cnt)556 _ctf_drop_checks(struct tcpopt *to, struct mbuf *m, struct tcphdr *th,
557 struct tcpcb *tp, int32_t *tlenp,
558 int32_t *thf, int32_t *drop_hdrlen, int32_t *ret_val,
559 uint32_t *ts, uint32_t *cnt)
560 {
561 int32_t todrop;
562 int32_t thflags;
563 int32_t tlen;
564
565 thflags = *thf;
566 tlen = *tlenp;
567 todrop = tp->rcv_nxt - th->th_seq;
568 if (todrop > 0) {
569 if (thflags & TH_SYN) {
570 thflags &= ~TH_SYN;
571 th->th_seq++;
572 if (th->th_urp > 1)
573 th->th_urp--;
574 else
575 thflags &= ~TH_URG;
576 todrop--;
577 }
578 /*
579 * Following if statement from Stevens, vol. 2, p. 960.
580 */
581 if (todrop > tlen
582 || (todrop == tlen && (thflags & TH_FIN) == 0)) {
583 /*
584 * Any valid FIN must be to the left of the window.
585 * At this point the FIN must be a duplicate or out
586 * of sequence; drop it.
587 */
588 thflags &= ~TH_FIN;
589 /*
590 * Send an ACK to resynchronize and drop any data.
591 * But keep on processing for RST or ACK.
592 */
593 ctf_ack_war_checks(tp, ts, cnt);
594 todrop = tlen;
595 KMOD_TCPSTAT_INC(tcps_rcvduppack);
596 KMOD_TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
597 } else {
598 KMOD_TCPSTAT_INC(tcps_rcvpartduppack);
599 KMOD_TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
600 }
601 /*
602 * DSACK - add SACK block for dropped range
603 */
604 if ((todrop > 0) && (tp->t_flags & TF_SACK_PERMIT)) {
605 /*
606 * ACK now, as the next in-sequence segment
607 * will clear the DSACK block again
608 */
609 ctf_ack_war_checks(tp, ts, cnt);
610 if (tp->t_flags & TF_ACKNOW)
611 tcp_update_sack_list(tp, th->th_seq,
612 th->th_seq + todrop);
613 }
614 *drop_hdrlen += todrop; /* drop from the top afterwards */
615 th->th_seq += todrop;
616 tlen -= todrop;
617 if (th->th_urp > todrop)
618 th->th_urp -= todrop;
619 else {
620 thflags &= ~TH_URG;
621 th->th_urp = 0;
622 }
623 }
624 /*
625 * If segment ends after window, drop trailing data (and PUSH and
626 * FIN); if nothing left, just ACK.
627 */
628 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
629 if (todrop > 0) {
630 KMOD_TCPSTAT_INC(tcps_rcvpackafterwin);
631 if (todrop >= tlen) {
632 KMOD_TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
633 /*
634 * If window is closed can only take segments at
635 * window edge, and have to drop data and PUSH from
636 * incoming segments. Continue processing, but
637 * remember to ack. Otherwise, drop segment and
638 * ack.
639 */
640 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
641 ctf_ack_war_checks(tp, ts, cnt);
642 KMOD_TCPSTAT_INC(tcps_rcvwinprobe);
643 } else {
644 __ctf_do_dropafterack(m, tp, th, thflags, tlen, ret_val, ts, cnt);
645 return (1);
646 }
647 } else
648 KMOD_TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
649 m_adj(m, -todrop);
650 tlen -= todrop;
651 thflags &= ~(TH_PUSH | TH_FIN);
652 }
653 *thf = thflags;
654 *tlenp = tlen;
655 return (0);
656 }
657
658 /*
659 * The value in ret_val informs the caller
660 * if we dropped the tcb (and lock) or not.
661 * 1 = we dropped it, 0 = the TCB is still locked
662 * and valid.
663 */
664 void
__ctf_do_dropafterack(struct mbuf * m,struct tcpcb * tp,struct tcphdr * th,int32_t thflags,int32_t tlen,int32_t * ret_val,uint32_t * ts,uint32_t * cnt)665 __ctf_do_dropafterack(struct mbuf *m, struct tcpcb *tp, struct tcphdr *th, int32_t thflags, int32_t tlen, int32_t *ret_val, uint32_t *ts, uint32_t *cnt)
666 {
667 /*
668 * Generate an ACK dropping incoming segment if it occupies sequence
669 * space, where the ACK reflects our state.
670 *
671 * We can now skip the test for the RST flag since all paths to this
672 * code happen after packets containing RST have been dropped.
673 *
674 * In the SYN-RECEIVED state, don't send an ACK unless the segment
675 * we received passes the SYN-RECEIVED ACK test. If it fails send a
676 * RST. This breaks the loop in the "LAND" DoS attack, and also
677 * prevents an ACK storm between two listening ports that have been
678 * sent forged SYN segments, each with the source address of the
679 * other.
680 */
681 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
682 (SEQ_GT(tp->snd_una, th->th_ack) ||
683 SEQ_GT(th->th_ack, tp->snd_max))) {
684 *ret_val = 1;
685 ctf_do_dropwithreset(m, tp, th, BANDLIM_RST_OPENPORT, tlen);
686 return;
687 } else
688 *ret_val = 0;
689 ctf_ack_war_checks(tp, ts, cnt);
690 if (m)
691 m_freem(m);
692 }
693
694 void
ctf_do_drop(struct mbuf * m,struct tcpcb * tp)695 ctf_do_drop(struct mbuf *m, struct tcpcb *tp)
696 {
697
698 /*
699 * Drop space held by incoming segment and return.
700 */
701 if (tp != NULL)
702 INP_WUNLOCK(tptoinpcb(tp));
703 if (m)
704 m_freem(m);
705 }
706
707 int
__ctf_process_rst(struct mbuf * m,struct tcphdr * th,struct socket * so,struct tcpcb * tp,uint32_t * ts,uint32_t * cnt)708 __ctf_process_rst(struct mbuf *m, struct tcphdr *th, struct socket *so,
709 struct tcpcb *tp, uint32_t *ts, uint32_t *cnt)
710 {
711 /*
712 * RFC5961 Section 3.2
713 *
714 * - RST drops connection only if SEG.SEQ == RCV.NXT. - If RST is in
715 * window, we send challenge ACK.
716 *
717 * Note: to take into account delayed ACKs, we should test against
718 * last_ack_sent instead of rcv_nxt. Note 2: we handle special case
719 * of closed window, not covered by the RFC.
720 */
721 int dropped = 0;
722
723 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
724 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
725 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
726 KASSERT(tp->t_state != TCPS_SYN_SENT,
727 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p",
728 __func__, th, tp));
729
730 if (V_tcp_insecure_rst ||
731 (tp->last_ack_sent == th->th_seq) ||
732 (tp->rcv_nxt == th->th_seq)) {
733 KMOD_TCPSTAT_INC(tcps_drops);
734 /* Drop the connection. */
735 switch (tp->t_state) {
736 case TCPS_SYN_RECEIVED:
737 so->so_error = ECONNREFUSED;
738 goto close;
739 case TCPS_ESTABLISHED:
740 case TCPS_FIN_WAIT_1:
741 case TCPS_FIN_WAIT_2:
742 case TCPS_CLOSE_WAIT:
743 case TCPS_CLOSING:
744 case TCPS_LAST_ACK:
745 so->so_error = ECONNRESET;
746 close:
747 tcp_state_change(tp, TCPS_CLOSED);
748 /* FALLTHROUGH */
749 default:
750 tcp_log_end_status(tp, TCP_EI_STATUS_CLIENT_RST);
751 tp = tcp_close(tp);
752 }
753 dropped = 1;
754 ctf_do_drop(m, tp);
755 } else {
756 int send_challenge;
757
758 KMOD_TCPSTAT_INC(tcps_badrst);
759 if ((ts != NULL) && (cnt != NULL) &&
760 (V_tcp_ack_war_time_window > 0) &&
761 (V_tcp_ack_war_cnt > 0)) {
762 /* We are possibly preventing an ack-rst war prevention */
763 uint32_t cts;
764
765 /*
766 * We use a msec tick here which gives us
767 * roughly 49 days. We don't need the
768 * precision of a microsecond timestamp which
769 * would only give us hours.
770 */
771 cts = tcp_ts_getticks();
772 if (TSTMP_LT((*ts), cts)) {
773 /* Timestamp is in the past */
774 *cnt = 0;
775 *ts = (cts + V_tcp_ack_war_time_window);
776 }
777 if (*cnt < V_tcp_ack_war_cnt) {
778 *cnt = (*cnt + 1);
779 send_challenge = 1;
780 } else
781 send_challenge = 0;
782 } else
783 send_challenge = 1;
784 if (send_challenge) {
785 /* Send challenge ACK. */
786 tcp_respond(tp, mtod(m, void *), th, m,
787 tp->rcv_nxt, tp->snd_nxt, TH_ACK);
788 tp->last_ack_sent = tp->rcv_nxt;
789 }
790 }
791 } else {
792 m_freem(m);
793 }
794 return (dropped);
795 }
796
797 /*
798 * The value in ret_val informs the caller
799 * if we dropped the tcb (and lock) or not.
800 * 1 = we dropped it, 0 = the TCB is still locked
801 * and valid.
802 */
803 void
ctf_challenge_ack(struct mbuf * m,struct tcphdr * th,struct tcpcb * tp,uint8_t iptos,int32_t * ret_val)804 ctf_challenge_ack(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, uint8_t iptos, int32_t * ret_val)
805 {
806
807 NET_EPOCH_ASSERT();
808
809 KMOD_TCPSTAT_INC(tcps_badsyn);
810 if (V_tcp_insecure_syn &&
811 SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
812 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
813 tp = tcp_drop(tp, ECONNRESET);
814 *ret_val = 1;
815 ctf_do_drop(m, tp);
816 } else {
817 tcp_ecn_input_syn_sent(tp, tcp_get_flags(th), iptos);
818 /* Send challenge ACK. */
819 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt,
820 tp->snd_nxt, TH_ACK);
821 tp->last_ack_sent = tp->rcv_nxt;
822 m = NULL;
823 *ret_val = 0;
824 ctf_do_drop(m, NULL);
825 }
826 }
827
828 /*
829 * ctf_ts_check returns 1 for you should not proceed, the state
830 * machine should return. It places in ret_val what should
831 * be returned 1/0 by the caller (hpts_do_segment). The 1 indicates
832 * that the TCB is unlocked and probably dropped. The 0 indicates the
833 * TCB is still valid and locked.
834 */
835 int
ctf_ts_check(struct mbuf * m,struct tcphdr * th,struct tcpcb * tp,int32_t tlen,int32_t thflags,int32_t * ret_val)836 ctf_ts_check(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
837 int32_t tlen, int32_t thflags, int32_t * ret_val)
838 {
839
840 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
841 /*
842 * Invalidate ts_recent. If this segment updates ts_recent,
843 * the age will be reset later and ts_recent will get a
844 * valid value. If it does not, setting ts_recent to zero
845 * will at least satisfy the requirement that zero be placed
846 * in the timestamp echo reply when ts_recent isn't valid.
847 * The age isn't reset until we get a valid ts_recent
848 * because we don't want out-of-order segments to be dropped
849 * when ts_recent is old.
850 */
851 tp->ts_recent = 0;
852 } else {
853 KMOD_TCPSTAT_INC(tcps_rcvduppack);
854 KMOD_TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
855 KMOD_TCPSTAT_INC(tcps_pawsdrop);
856 *ret_val = 0;
857 if (tlen) {
858 ctf_do_dropafterack(m, tp, th, thflags, tlen, ret_val);
859 } else {
860 ctf_do_drop(m, NULL);
861 }
862 return (1);
863 }
864 return (0);
865 }
866
867 int
ctf_ts_check_ac(struct tcpcb * tp,int32_t thflags)868 ctf_ts_check_ac(struct tcpcb *tp, int32_t thflags)
869 {
870
871 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) {
872 /*
873 * Invalidate ts_recent. If this segment updates ts_recent,
874 * the age will be reset later and ts_recent will get a
875 * valid value. If it does not, setting ts_recent to zero
876 * will at least satisfy the requirement that zero be placed
877 * in the timestamp echo reply when ts_recent isn't valid.
878 * The age isn't reset until we get a valid ts_recent
879 * because we don't want out-of-order segments to be dropped
880 * when ts_recent is old.
881 */
882 tp->ts_recent = 0;
883 } else {
884 KMOD_TCPSTAT_INC(tcps_rcvduppack);
885 KMOD_TCPSTAT_INC(tcps_pawsdrop);
886 return (1);
887 }
888 return (0);
889 }
890
891
892
893 void
ctf_calc_rwin(struct socket * so,struct tcpcb * tp)894 ctf_calc_rwin(struct socket *so, struct tcpcb *tp)
895 {
896 int32_t win;
897
898 /*
899 * Calculate amount of space in receive window, and then do TCP
900 * input processing. Receive window is amount of space in rcv queue,
901 * but not less than advertised window.
902 */
903 win = sbspace(&so->so_rcv);
904 if (win < 0)
905 win = 0;
906 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
907 }
908
909 void
ctf_do_dropwithreset_conn(struct mbuf * m,struct tcpcb * tp,struct tcphdr * th,int32_t rstreason,int32_t tlen)910 ctf_do_dropwithreset_conn(struct mbuf *m, struct tcpcb *tp, struct tcphdr *th,
911 int32_t rstreason, int32_t tlen)
912 {
913
914 tcp_dropwithreset(m, th, tp, tlen, rstreason);
915 tp = tcp_drop(tp, ETIMEDOUT);
916 if (tp)
917 INP_WUNLOCK(tptoinpcb(tp));
918 }
919
920 uint32_t
ctf_fixed_maxseg(struct tcpcb * tp)921 ctf_fixed_maxseg(struct tcpcb *tp)
922 {
923 return (tcp_fixed_maxseg(tp));
924 }
925
926 void
ctf_log_sack_filter(struct tcpcb * tp,int num_sack_blks,struct sackblk * sack_blocks)927 ctf_log_sack_filter(struct tcpcb *tp, int num_sack_blks, struct sackblk *sack_blocks)
928 {
929 if (tcp_bblogging_on(tp)) {
930 union tcp_log_stackspecific log;
931 struct timeval tv;
932
933 memset(&log, 0, sizeof(log));
934 log.u_bbr.timeStamp = tcp_get_usecs(&tv);
935 log.u_bbr.flex8 = num_sack_blks;
936 if (num_sack_blks > 0) {
937 log.u_bbr.flex1 = sack_blocks[0].start;
938 log.u_bbr.flex2 = sack_blocks[0].end;
939 }
940 if (num_sack_blks > 1) {
941 log.u_bbr.flex3 = sack_blocks[1].start;
942 log.u_bbr.flex4 = sack_blocks[1].end;
943 }
944 if (num_sack_blks > 2) {
945 log.u_bbr.flex5 = sack_blocks[2].start;
946 log.u_bbr.flex6 = sack_blocks[2].end;
947 }
948 if (num_sack_blks > 3) {
949 log.u_bbr.applimited = sack_blocks[3].start;
950 log.u_bbr.pkts_out = sack_blocks[3].end;
951 }
952 TCP_LOG_EVENTP(tp, NULL,
953 &tptosocket(tp)->so_rcv,
954 &tptosocket(tp)->so_snd,
955 TCP_SACK_FILTER_RES, 0,
956 0, &log, false, &tv);
957 }
958 }
959
960 uint32_t
ctf_decay_count(uint32_t count,uint32_t decay)961 ctf_decay_count(uint32_t count, uint32_t decay)
962 {
963 /*
964 * Given a count, decay it by a set percentage. The
965 * percentage is in thousands i.e. 100% = 1000,
966 * 19.3% = 193.
967 */
968 uint64_t perc_count, decay_per;
969 uint32_t decayed_count;
970 if (decay > 1000) {
971 /* We don't raise it */
972 return (count);
973 }
974 perc_count = count;
975 decay_per = decay;
976 perc_count *= decay_per;
977 perc_count /= 1000;
978 /*
979 * So now perc_count holds the
980 * count decay value.
981 */
982 decayed_count = count - (uint32_t)perc_count;
983 return(decayed_count);
984 }
985
986 int32_t
ctf_progress_timeout_check(struct tcpcb * tp,bool log)987 ctf_progress_timeout_check(struct tcpcb *tp, bool log)
988 {
989 if (tp->t_maxunacktime && tp->t_acktime && TSTMP_GT(ticks, tp->t_acktime)) {
990 if ((ticks - tp->t_acktime) >= tp->t_maxunacktime) {
991 /*
992 * There is an assumption that the caller
993 * will drop the connection so we will
994 * increment the counters here.
995 */
996 if (log)
997 tcp_log_end_status(tp, TCP_EI_STATUS_PROGRESS);
998 #ifdef NETFLIX_STATS
999 KMOD_TCPSTAT_INC(tcps_progdrops);
1000 #endif
1001 return (1);
1002 }
1003 }
1004 return (0);
1005 }
1006