mdw@git.distorted.org.uk Git - secnet/blob - util.c

   1 /*
   2  * util.c
   3  * - output and logging support
   4  * - program lifetime support
   5  * - IP address and subnet munging routines
   6  * - MPI convenience functions
   7  */
   8 /*
   9  * This file is part of secnet.
  10  * See README for full list of copyright holders.
  11  *
  12  * secnet is free software; you can redistribute it and/or modify it
  13  * under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 3 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * secnet is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * version 3 along with secnet; if not, see
  24  * https://www.gnu.org/licenses/gpl.html.
  25  */
  26
  27 #include "secnet.h"
  28 #include <stdio.h>
  29 #include <string.h>
  30 #include <errno.h>
  31 #include <unistd.h>
  32 #include <limits.h>
  33 #include <assert.h>
  34 #include <sys/wait.h>
  35 #include <adns.h>
  36 #include "util.h"
  37 #include "unaligned.h"
  38 #include "magic.h"
  39 #include "ipaddr.h"
  40
  41 #define MIN_BUFFER_SIZE 64
  42 #define DEFAULT_BUFFER_SIZE 4096
  43 #define MAX_BUFFER_SIZE 131072
  44
  45 static const char *hexdigits="0123456789abcdef";
  46
  47 uint32_t current_phase=0;
  48
  49 struct phase_hook {
  50     hook_fn *fn;
  51     void *state;
  52     LIST_ENTRY(phase_hook) entry;
  53 };
  54
  55 static LIST_HEAD(, phase_hook) hooks[NR_PHASES];
  56
  57 char *safe_strdup(const char *s, const char *message)
  58 {
  59     char *d;
  60     d=strdup(s);
  61     if (!d) {
  62         fatal_perror("%s",message);
  63     }
  64     return d;
  65 }
  66
  67 void *safe_malloc(size_t size, const char *message)
  68 {
  69     void *r;
  70     if (!size)
  71         return 0;
  72     r=malloc(size);
  73     if (!r) {
  74         fatal_perror("%s",message);
  75     }
  76     return r;
  77 }
  78 void *safe_realloc_ary(void *p, size_t size, size_t count,
  79                        const char *message) {
  80     if (count >= INT_MAX/size) {
  81         fatal("array allocation overflow: %s", message);
  82     }
  83     assert(size && count);
  84     p = realloc(p, size*count);
  85     if (!p)
  86         fatal_perror("%s", message);
  87     return p;
  88 }
  89
  90 void *safe_malloc_ary(size_t size, size_t count, const char *message) {
  91     if (!size || !count)
  92         return 0;
  93     return safe_realloc_ary(0,size,count,message);
  94 }
  95
  96 void hex_encode(const uint8_t *bin, int binsize, char *buff)
  97 {
  98     int i;
  99
 100     for (i=0; i<binsize; i++) {
 101         buff[i*2]=hexdigits[(bin[i] & 0xf0) >> 4];
 102         buff[i*2+1]=hexdigits[(bin[i] & 0xf)];
 103     }
 104     buff[binsize*2]=0;
 105 }
 106
 107 string_t hex_encode_alloc(const uint8_t *bin, int binsize)
 108 {
 109     char *buff;
 110
 111     buff=safe_malloc(hex_encode_size(binsize),"hex_encode");
 112     hex_encode(bin,binsize,buff);
 113     return buff;
 114 }
 115
 116 static uint8_t hexval(uint8_t c)
 117 {
 118     switch (c) {
 119     case '0': return 0;
 120     case '1': return 1;
 121     case '2': return 2;
 122     case '3': return 3;
 123     case '4': return 4;
 124     case '5': return 5;
 125     case '6': return 6;
 126     case '7': return 7;
 127     case '8': return 8;
 128     case '9': return 9;
 129     case 'a': return 10;
 130     case 'A': return 10;
 131     case 'b': return 11;
 132     case 'B': return 11;
 133     case 'c': return 12;
 134     case 'C': return 12;
 135     case 'd': return 13;
 136     case 'D': return 13;
 137     case 'e': return 14;
 138     case 'E': return 14;
 139     case 'f': return 15;
 140     case 'F': return 15;
 141     }
 142     return -1;
 143 }
 144
 145 bool_t hex_decode(uint8_t *buffer, int32_t buflen, int32_t *outlen,
 146                   cstring_t hb, bool_t allow_odd_nibble)
 147 {
 148     int i = 0, j = 0, l = strlen(hb), hi, lo;
 149     bool_t ok = False;
 150
 151     if (!l || !buflen) { ok = !l; goto done; }
 152     if (l&1) {
 153         /* The number starts with a half-byte */
 154         if (!allow_odd_nibble) goto done;
 155         lo = hexval(hb[j++]); if (lo < 0) goto done;
 156         buffer[i++] = lo;
 157     }
 158     for (; hb[j] && i < buflen; i++) {
 159         hi = hexval(hb[j++]);
 160         lo = hexval(hb[j++]);
 161         if (hi < 0 || lo < 0) goto done;
 162         buffer[i] = (hi << 4) | lo;
 163     }
 164     ok = !hb[j];
 165 done:
 166     *outlen = i;
 167     return ok;
 168 }
 169
 170 void read_mpbin(MP_INT *a, uint8_t *bin, int binsize)
 171 {
 172     char *buff = hex_encode_alloc(bin, binsize);
 173     mpz_set_str(a, buff, 16);
 174     free(buff);
 175 }
 176
 177 char *write_mpstring(MP_INT *a)
 178 {
 179     char *buff;
 180
 181     buff=safe_malloc(mpz_sizeinbase(a,16)+2,"write_mpstring");
 182     mpz_get_str(buff, 16, a);
 183     return buff;
 184 }
 185
 186 int32_t write_mpbin(MP_INT *a, uint8_t *buffer, int32_t buflen)
 187 {
 188     char *hb = write_mpstring(a);
 189     int32_t len;
 190     hex_decode(buffer, buflen, &len, hb, True);
 191     free(hb);
 192     return len;
 193 }
 194
 195 #define DEFINE_SETFDFLAG(fn,FL,FLAG)                                    \
 196 void fn(int fd) {                                                       \
 197     int r=fcntl(fd, F_GET##FL);                                         \
 198     if (r<0) fatal_perror("fcntl(,F_GET" #FL ") failed");               \
 199     r=fcntl(fd, F_SET##FL, r|FLAG);                                     \
 200     if (r<0) fatal_perror("fcntl(,F_SET" #FL ",|" #FLAG ") failed");    \
 201 }
 202
 203 DEFINE_SETFDFLAG(setcloexec,FD,FD_CLOEXEC);
 204 DEFINE_SETFDFLAG(setnonblock,FL,O_NONBLOCK);
 205
 206 void pipe_cloexec(int fd[2]) {
 207     int r=pipe(fd);
 208     if (r) fatal_perror("pipe");
 209     setcloexec(fd[0]);
 210     setcloexec(fd[1]);
 211 }
 212
 213 static const char *phases[NR_PHASES]={
 214     "PHASE_INIT",
 215     "PHASE_GETOPTS",
 216     "PHASE_READCONFIG",
 217     "PHASE_SETUP",
 218     "PHASE_DAEMONIZE",
 219     "PHASE_GETRESOURCES",
 220     "PHASE_DROPPRIV",
 221     "PHASE_RUN",
 222     "PHASE_SHUTDOWN",
 223     "PHASE_CHILDPERSIST"
 224 };
 225
 226 void enter_phase(uint32_t new_phase)
 227 {
 228     struct phase_hook *i;
 229
 230     if (!LIST_EMPTY(&hooks[new_phase]))
 231         Message(M_DEBUG_PHASE,"Running hooks for %s...\n", phases[new_phase]);
 232     current_phase=new_phase;
 233
 234     LIST_FOREACH(i, &hooks[new_phase], entry)
 235         i->fn(i->state, new_phase);
 236     Message(M_DEBUG_PHASE,"Now in %s\n",phases[new_phase]);
 237 }
 238
 239 void phase_hooks_init(void)
 240 {
 241     int i;
 242     for (i=0; i<NR_PHASES; i++)
 243         LIST_INIT(&hooks[i]);
 244 }
 245
 246 void clear_phase_hooks(uint32_t phase)
 247 {
 248     struct phase_hook *h, *htmp;
 249     LIST_FOREACH_SAFE(h, &hooks[phase], entry, htmp)
 250         free(h);
 251     LIST_INIT(&hooks[phase]);
 252 }
 253
 254 bool_t add_hook(uint32_t phase, hook_fn *fn, void *state)
 255 {
 256     struct phase_hook *h;
 257
 258     NEW(h);
 259     h->fn=fn;
 260     h->state=state;
 261     LIST_INSERT_HEAD(&hooks[phase],h,entry);
 262     return True;
 263 }
 264
 265 bool_t remove_hook(uint32_t phase, hook_fn *fn, void *state)
 266 {
 267     fatal("remove_hook: not implemented");
 268
 269     return False;
 270 }
 271
 272 void vslilog(struct log_if *lf, int priority, const char *message, va_list ap)
 273 {
 274     lf->vlogfn(lf->st,priority,message,ap);
 275 }
 276
 277 void slilog(struct log_if *lf, int priority, const char *message, ...)
 278 {
 279     va_list ap;
 280
 281     va_start(ap,message);
 282     vslilog(lf,priority,message,ap);
 283     va_end(ap);
 284 }
 285
 286 struct buffer {
 287     closure_t cl;
 288     struct buffer_if ops;
 289 };
 290
 291 void buffer_assert_free(struct buffer_if *buffer, cstring_t file,
 292                         int line)
 293 {
 294     if (!buffer->free) {
 295         fprintf(stderr,"secnet: BUF_ASSERT_FREE, %s line %d, owned by %s",
 296                 file,line,buffer->owner);
 297         assert(!"buffer_assert_free failure");
 298     }
 299 }
 300
 301 void buffer_assert_used(struct buffer_if *buffer, cstring_t file,
 302                         int line)
 303 {
 304     if (buffer->free) {
 305         fprintf(stderr,"secnet: BUF_ASSERT_USED, %s line %d, last owned by %s",
 306                 file,line,buffer->owner);
 307         assert(!"buffer_assert_used failure");
 308     }
 309 }
 310
 311 void buffer_init(struct buffer_if *buffer, int32_t max_start_pad)
 312 {
 313     assert(max_start_pad<=buffer->alloclen);
 314     buffer->start=buffer->base+max_start_pad;
 315     buffer->size=0;
 316 }
 317
 318 void buffer_destroy(struct buffer_if *buf)
 319 {
 320     BUF_ASSERT_FREE(buf);
 321     free(buf->base);
 322     buf->start=buf->base=0;
 323     buf->size=buf->alloclen=0;
 324 }
 325
 326 void *buf_append(struct buffer_if *buf, int32_t amount) {
 327     void *p;
 328     assert(amount <= buf_remaining_space(buf));
 329     p=buf->start + buf->size;
 330     buf->size+=amount;
 331     return p;
 332 }
 333
 334 void *buf_prepend(struct buffer_if *buf, int32_t amount) {
 335     assert(amount <= buf->start - buf->base);
 336     buf->size+=amount;
 337     return buf->start-=amount;
 338 }
 339
 340 void *buf_unappend(struct buffer_if *buf, int32_t amount) {
 341     if (buf->size < amount) return 0;
 342     return buf->start+(buf->size-=amount);
 343 }
 344
 345 void *buf_unprepend(struct buffer_if *buf, int32_t amount) {
 346     void *p;
 347     if (buf->size < amount) return 0;
 348     p=buf->start;
 349     buf->start+=amount;
 350     buf->size-=amount;
 351     return p;
 352 }
 353
 354 void buf_append_string(struct buffer_if *buf, cstring_t s)
 355 {
 356     size_t len;
 357
 358     len=strlen(s);
 359     /* fixme: if string is longer than 65535, result is a corrupted packet */
 360     buf_append_uint16(buf,len);
 361     BUF_ADD_BYTES(append,buf,s,len);
 362 }
 363
 364 void buffer_new(struct buffer_if *buf, int32_t len)
 365 {
 366     buf->free=True;
 367     buf->owner=NULL;
 368     buf->flags=0;
 369     buf->loc.file=NULL;
 370     buf->loc.line=0;
 371     buf->size=0;
 372     buf->alloclen=len;
 373     buf->start=NULL;
 374     buf->base=safe_malloc(len,"buffer_new");
 375 }
 376
 377 void buffer_readonly_view(struct buffer_if *buf, const void *data, int32_t len)
 378 {
 379     buf->free=False;
 380     buf->owner="READONLY";
 381     buf->flags=0;
 382     buf->loc.file=NULL;
 383     buf->loc.line=0;
 384     buf->size=buf->alloclen=len;
 385     buf->base=buf->start=(uint8_t*)data;
 386 }
 387
 388 void buffer_readonly_clone(struct buffer_if *out, const struct buffer_if *in)
 389 {
 390     buffer_readonly_view(out,in->start,in->size);
 391 }
 392
 393 void buffer_copy(struct buffer_if *dst, const struct buffer_if *src)
 394 {
 395     if (dst->alloclen < src->alloclen) {
 396         dst->base=realloc(dst->base,src->alloclen);
 397         if (!dst->base) fatal_perror("buffer_copy");
 398         dst->alloclen = src->alloclen;
 399     }
 400     dst->start = dst->base + (src->start - src->base);
 401     dst->size = src->size;
 402     memcpy(dst->start, src->start, dst->size);
 403 }
 404
 405 static list_t *buffer_apply(closure_t *self, struct cloc loc, dict_t *context,
 406                             list_t *args)
 407 {
 408     struct buffer *st;
 409     item_t *item;
 410     dict_t *dict;
 411     bool_t lockdown=False;
 412     uint32_t len=DEFAULT_BUFFER_SIZE;
 413
 414     NEW(st);
 415     st->cl.description="buffer";
 416     st->cl.type=CL_BUFFER;
 417     st->cl.apply=NULL;
 418     st->cl.interface=&st->ops;
 419
 420     /* First argument, if present, is buffer length */
 421     item=list_elem(args,0);
 422     if (item) {
 423         if (item->type!=t_number) {
 424             cfgfatal(st->ops.loc,"buffer","first parameter must be a "
 425                      "number (buffer size)\n");
 426         }
 427         len=item->data.number;
 428         if (len<MIN_BUFFER_SIZE) {
 429             cfgfatal(st->ops.loc,"buffer","ludicrously small buffer size\n");
 430         }
 431         if (len>MAX_BUFFER_SIZE) {
 432             cfgfatal(st->ops.loc,"buffer","ludicrously large buffer size\n");
 433         }
 434     }
 435     /* Second argument, if present, is a dictionary */
 436     item=list_elem(args,1);
 437     if (item) {
 438         if (item->type!=t_dict) {
 439             cfgfatal(st->ops.loc,"buffer","second parameter must be a "
 440                      "dictionary\n");
 441         }
 442         dict=item->data.dict;
 443         lockdown=dict_read_bool(dict,"lockdown",False,"buffer",st->ops.loc,
 444                                 False);
 445     }
 446
 447     buffer_new(&st->ops,len);
 448     if (lockdown) {
 449         /* XXX mlock the buffer if possible */
 450     }
 451
 452     return new_closure(&st->cl);
 453 }
 454
 455 void send_nak(const struct comm_addr *dest, uint32_t our_index,
 456               uint32_t their_index, uint32_t msgtype,
 457               struct buffer_if *buf, const char *logwhy)
 458 {
 459     buffer_init(buf,calculate_max_start_pad());
 460     buf_append_uint32(buf,their_index);
 461     buf_append_uint32(buf,our_index);
 462     buf_append_uint32(buf,LABEL_NAK);
 463     if (logwhy)
 464         Message(M_INFO,"%s: %08"PRIx32"<-%08"PRIx32": %08"PRIx32":"
 465                 " %s; sending NAK\n",
 466                 comm_addr_to_string(dest),
 467                 our_index, their_index, msgtype, logwhy);
 468     dest->comm->sendmsg(dest->comm->st, buf, dest, 0);
 469 }
 470
 471 int consttime_memeq(const void *s1in, const void *s2in, size_t n)
 472 {
 473     const uint8_t *s1=s1in, *s2=s2in;
 474     register volatile uint8_t accumulator=0;
 475
 476     while (n-- > 0) {
 477         accumulator |= (*s1++ ^ *s2++);
 478     }
 479     accumulator |= accumulator >> 4; /* constant-time             */
 480     accumulator |= accumulator >> 2; /*  boolean canonicalisation */
 481     accumulator |= accumulator >> 1;
 482     accumulator &= 1;
 483     accumulator ^= 1;
 484     return accumulator;
 485 }
 486
 487 void util_module(dict_t *dict)
 488 {
 489     add_closure(dict,"sysbuffer",buffer_apply);
 490 }
 491
 492 void update_max_start_pad(int32_t *our_module_global, int32_t our_instance)
 493 {
 494     if (*our_module_global < our_instance)
 495         *our_module_global=our_instance;
 496 }
 497
 498 int32_t transform_max_start_pad, comm_max_start_pad;
 499
 500 int32_t calculate_max_start_pad(void)
 501 {
 502     return
 503         site_max_start_pad +
 504         transform_max_start_pad +
 505         comm_max_start_pad;
 506 }
 507
 508 void vslilog_part(struct log_if *lf, int priority, const char *message, va_list ap)
 509 {
 510     char *buff=lf->buff;
 511     size_t bp;
 512     char *nlp;
 513
 514     bp=strlen(buff);
 515     assert(bp < LOG_MESSAGE_BUFLEN);
 516     vsnprintf(buff+bp,LOG_MESSAGE_BUFLEN-bp,message,ap);
 517     buff[LOG_MESSAGE_BUFLEN-1] = '\n';
 518     buff[LOG_MESSAGE_BUFLEN] = '\0';
 519     /* Each line is sent separately */
 520     while ((nlp=strchr(buff,'\n'))) {
 521         *nlp=0;
 522         slilog(lf,priority,"%s",buff);
 523         memmove(buff,nlp+1,strlen(nlp+1)+1);
 524     }
 525 }
 526
 527 extern void slilog_part(struct log_if *lf, int priority, const char *message, ...)
 528 {
 529     va_list ap;
 530     va_start(ap,message);
 531     vslilog_part(lf,priority,message,ap);
 532     va_end(ap);
 533 }
 534
 535 void string_item_to_iaddr(const item_t *item, uint16_t port, union iaddr *ia,
 536                           const char *desc)
 537 {
 538 #ifndef CONFIG_IPV6
 539
 540     ia->sin.sin_family=AF_INET;
 541     ia->sin.sin_addr.s_addr=htonl(string_item_to_ipaddr(item,desc));
 542     ia->sin.sin_port=htons(port);
 543
 544 #else /* CONFIG_IPV6 => we have adns_text2addr */
 545
 546     if (item->type!=t_string)
 547         cfgfatal(item->loc,desc,"expecting a string IP (v4 or v6) address\n");
 548     socklen_t salen=sizeof(*ia);
 549     int r=adns_text2addr(item->data.string, port,
 550                          adns_qf_addrlit_ipv4_quadonly,
 551                          &ia->sa, &salen);
 552     assert(r!=ENOSPC);
 553     if (r) cfgfatal(item->loc,desc,"invalid IP (v4 or v6) address: %s\n",
 554                     strerror(r));
 555
 556 #endif /* CONFIG_IPV6 */
 557 }
 558
 559 #define IADDR_NBUFS 8
 560
 561 const char *iaddr_to_string(const union iaddr *ia)
 562 {
 563 #ifndef CONFIG_IPV6
 564
 565     SBUF_DEFINE(IADDR_NBUFS, 100);
 566
 567     assert(ia->sa.sa_family == AF_INET);
 568
 569     snprintf(SBUF, sizeof(SBUF), "[%s]:%d",
 570              inet_ntoa(ia->sin.sin_addr),
 571              ntohs(ia->sin.sin_port));
 572
 573 #else /* CONFIG_IPV6 => we have adns_addr2text */
 574
 575     SBUF_DEFINE(IADDR_NBUFS, 1+ADNS_ADDR2TEXT_BUFLEN+20);
 576
 577     int port;
 578
 579     char *addrbuf = SBUF;
 580     *addrbuf++ = '[';
 581     int addrbuflen = ADNS_ADDR2TEXT_BUFLEN;
 582
 583     int r = adns_addr2text(&ia->sa, 0, addrbuf, &addrbuflen, &port);
 584     if (r) {
 585         const char fmt[]= "scoped IPv6 addr, error: %.*s";
 586         sprintf(addrbuf, fmt,
 587                 (int)(ADNS_ADDR2TEXT_BUFLEN - sizeof(fmt)) /* underestimate */,
 588                 strerror(r));
 589     }
 590
 591     char *portbuf = addrbuf;
 592     int addrl = strlen(addrbuf);
 593     portbuf += addrl;
 594
 595     snprintf(portbuf, sizeof(SBUF)-addrl, "]:%d", port);
 596
 597 #endif /* CONFIG_IPV6 */
 598
 599     return SBUF;
 600 }
 601
 602 bool_t iaddr_equal(const union iaddr *ia, const union iaddr *ib,
 603                    bool_t ignoreport)
 604 {
 605     if (ia->sa.sa_family != ib->sa.sa_family)
 606         return 0;
 607     switch (ia->sa.sa_family) {
 608     case AF_INET:
 609         return ia->sin.sin_addr.s_addr == ib->sin.sin_addr.s_addr
 610            && (ignoreport ||
 611                ia->sin.sin_port        == ib->sin.sin_port);
 612 #ifdef CONFIG_IPV6
 613     case AF_INET6:
 614         return !memcmp(&ia->sin6.sin6_addr, &ib->sin6.sin6_addr, 16)
 615            &&  ia->sin6.sin6_scope_id  == ib->sin6.sin6_scope_id
 616            && (ignoreport ||
 617                ia->sin6.sin6_port      == ib->sin6.sin6_port)
 618             /* we ignore the flowinfo field */;
 619 #endif /* CONFIG_IPV6 */
 620     default:
 621         abort();
 622     }
 623 }
 624
 625 int iaddr_socklen(const union iaddr *ia)
 626 {
 627     switch (ia->sa.sa_family) {
 628     case AF_INET:  return sizeof(ia->sin);
 629 #ifdef CONFIG_IPV6
 630     case AF_INET6: return sizeof(ia->sin6);
 631 #endif /* CONFIG_IPV6 */
 632     default:       abort();
 633     }
 634 }
 635
 636 const char *pollbadbit(int revents)
 637 {
 638 #define BADBIT(b) \
 639     if ((revents & b)) return #b
 640     BADBIT(POLLERR);
 641     BADBIT(POLLHUP);
 642     /* POLLNVAL is handled by the event loop - see afterpoll_fn comment */
 643 #undef BADBIT
 644     return 0;
 645 }
 646
 647 enum async_linebuf_result
 648 async_linebuf_read(struct pollfd *pfd, struct buffer_if *buf,
 649                    const char **emsg_out)
 650 {
 651     int revents=pfd->revents;
 652
 653 #define BAD(m) do{ *emsg_out=(m); return async_linebuf_broken; }while(0)
 654
 655     const char *badbit=pollbadbit(revents);
 656     if (badbit) BAD(badbit);
 657
 658     if (!(revents & POLLIN))
 659         return async_linebuf_nothing;
 660
 661     /*
 662      * Data structure: A line which has been returned to the user is
 663      * stored in buf at base before start.  But we retain the usual
 664      * buffer meaning of size.  So:
 665      *
 666      *   | returned :    | input read,   |    unused    |
 667      *   |  to user : \0 |  awaiting     |     buffer   |
 668      *   |          :    |  processing   |      space   |
 669      *   |          :    |               |              |
 670      *   ^base           ^start          ^start+size    ^base+alloclen
 671      */
 672
 673     BUF_ASSERT_USED(buf);
 674
 675     /* firstly, eat any previous */
 676     if (buf->start != buf->base) {
 677         memmove(buf->base,buf->start,buf->size);
 678         buf->start=buf->base;
 679     }
 680
 681     uint8_t *searched=buf->base;
 682
 683     /*
 684      * During the workings here we do not use start.  We set start
 685      * when we return some actual data.  So we have this:
 686      *
 687      *   | searched     | read, might   |  unused      |
 688      *   |  for \n      |  contain \n   |   buffer     |
 689      *   |  none found  |  but not \0   |    space     |
 690      *   |              |               |              |
 691      *   ^base          ^searched       ^base+size     ^base+alloclen
 692      *  [^start]                        ^dataend
 693      *
 694      */
 695     for (;;) {
 696         uint8_t *dataend=buf->base+buf->size;
 697         char *newline=memchr(searched,'\n',dataend-searched);
 698         if (newline) {
 699             *newline=0;
 700             buf->start=newline+1;
 701             buf->size=dataend-buf->start;
 702             return async_linebuf_ok;
 703         }
 704         searched=dataend;
 705         ssize_t space=(buf->base+buf->alloclen)-dataend;
 706         if (!space) BAD("input line too long");
 707         ssize_t r=read(pfd->fd,searched,space);
 708         if (r==0) {
 709             *searched=0;
 710             *emsg_out=buf->size?"no newline at eof":0;
 711             buf->start=searched+1;
 712             buf->size=0;
 713             return async_linebuf_eof;
 714         }
 715         if (r<0) {
 716             if (errno==EINTR)
 717                 continue;
 718             if (iswouldblock(errno))
 719                 return async_linebuf_nothing;
 720             BAD(strerror(errno));
 721         }
 722         assert(r<=space);
 723         if (memchr(searched,0,r)) BAD("nul in input data");
 724         buf->size+=r;
 725     }
 726
 727 #undef BAD
 728 }