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 /* Hex-encode a buffer, and return the hex in a freshly allocated string. */
  97 string_t hex_encode(const uint8_t *bin, int binsize)
  98 {
  99     char *buff;
 100     int i;
 101
 102     buff=safe_malloc(binsize*2 + 1,"hex_encode");
 103
 104     for (i=0; i<binsize; i++) {
 105         buff[i*2]=hexdigits[(bin[i] & 0xf0) >> 4];
 106         buff[i*2+1]=hexdigits[(bin[i] & 0xf)];
 107     }
 108     buff[binsize*2]=0;
 109     return buff;
 110 }
 111
 112 static uint8_t hexval(uint8_t c)
 113 {
 114     switch (c) {
 115     case '0': return 0;
 116     case '1': return 1;
 117     case '2': return 2;
 118     case '3': return 3;
 119     case '4': return 4;
 120     case '5': return 5;
 121     case '6': return 6;
 122     case '7': return 7;
 123     case '8': return 8;
 124     case '9': return 9;
 125     case 'a': return 10;
 126     case 'A': return 10;
 127     case 'b': return 11;
 128     case 'B': return 11;
 129     case 'c': return 12;
 130     case 'C': return 12;
 131     case 'd': return 13;
 132     case 'D': return 13;
 133     case 'e': return 14;
 134     case 'E': return 14;
 135     case 'f': return 15;
 136     case 'F': return 15;
 137     }
 138     return -1;
 139 }
 140
 141 bool_t hex_decode(uint8_t *buffer, int32_t buflen, int32_t *outlen,
 142                   cstring_t hb, bool_t allow_odd_nibble)
 143 {
 144     int i = 0, j = 0, l = strlen(hb), hi, lo;
 145     bool_t ok = False;
 146
 147     if (!l || !buflen) { ok = !l; goto done; }
 148     if (l&1) {
 149         /* The number starts with a half-byte */
 150         if (!allow_odd_nibble) goto done;
 151         lo = hexval(hb[j++]); if (lo < 0) goto done;
 152         buffer[i++] = lo;
 153     }
 154     for (; hb[j] && i < buflen; i++) {
 155         hi = hexval(hb[j++]);
 156         lo = hexval(hb[j++]);
 157         if (hi < 0 || lo < 0) goto done;
 158         buffer[i] = (hi << 4) | lo;
 159     }
 160     ok = !hb[j];
 161 done:
 162     *outlen = i;
 163     return ok;
 164 }
 165
 166 /* Convert a buffer into its MP_INT representation */
 167 void read_mpbin(MP_INT *a, uint8_t *bin, int binsize)
 168 {
 169     char *buff = hex_encode(bin, binsize);
 170     mpz_set_str(a, buff, 16);
 171     free(buff);
 172 }
 173
 174 /* Convert a MP_INT into a hex string */
 175 char *write_mpstring(MP_INT *a)
 176 {
 177     char *buff;
 178
 179     buff=safe_malloc(mpz_sizeinbase(a,16)+2,"write_mpstring");
 180     mpz_get_str(buff, 16, a);
 181     return buff;
 182 }
 183
 184 /* Convert a MP_INT into a buffer; return length; truncate if necessary */
 185 int32_t write_mpbin(MP_INT *a, uint8_t *buffer, int32_t buflen)
 186 {
 187     char *hb = write_mpstring(a);
 188     int32_t len;
 189     hex_decode(buffer, buflen, &len, hb, True);
 190     free(hb);
 191     return len;
 192 }
 193
 194 #define DEFINE_SETFDFLAG(fn,FL,FLAG)                                    \
 195 void fn(int fd) {                                                       \
 196     int r=fcntl(fd, F_GET##FL);                                         \
 197     if (r<0) fatal_perror("fcntl(,F_GET" #FL ") failed");               \
 198     r=fcntl(fd, F_SET##FL, r|FLAG);                                     \
 199     if (r<0) fatal_perror("fcntl(,F_SET" #FL ",|" #FLAG ") failed");    \
 200 }
 201
 202 DEFINE_SETFDFLAG(setcloexec,FD,FD_CLOEXEC);
 203 DEFINE_SETFDFLAG(setnonblock,FL,O_NONBLOCK);
 204
 205 void pipe_cloexec(int fd[2]) {
 206     int r=pipe(fd);
 207     if (r) fatal_perror("pipe");
 208     setcloexec(fd[0]);
 209     setcloexec(fd[1]);
 210 }
 211
 212 static const char *phases[NR_PHASES]={
 213     "PHASE_INIT",
 214     "PHASE_GETOPTS",
 215     "PHASE_READCONFIG",
 216     "PHASE_SETUP",
 217     "PHASE_DAEMONIZE",
 218     "PHASE_GETRESOURCES",
 219     "PHASE_DROPPRIV",
 220     "PHASE_RUN",
 221     "PHASE_SHUTDOWN",
 222     "PHASE_CHILDPERSIST"
 223 };
 224
 225 void enter_phase(uint32_t new_phase)
 226 {
 227     struct phase_hook *i;
 228
 229     if (!LIST_EMPTY(&hooks[new_phase]))
 230         Message(M_DEBUG_PHASE,"Running hooks for %s...\n", phases[new_phase]);
 231     current_phase=new_phase;
 232
 233     LIST_FOREACH(i, &hooks[new_phase], entry)
 234         i->fn(i->state, new_phase);
 235     Message(M_DEBUG_PHASE,"Now in %s\n",phases[new_phase]);
 236 }
 237
 238 void phase_hooks_init(void)
 239 {
 240     int i;
 241     for (i=0; i<NR_PHASES; i++)
 242         LIST_INIT(&hooks[i]);
 243 }
 244
 245 void clear_phase_hooks(uint32_t phase)
 246 {
 247     struct phase_hook *h, *htmp;
 248     LIST_FOREACH_SAFE(h, &hooks[phase], entry, htmp)
 249         free(h);
 250     LIST_INIT(&hooks[phase]);
 251 }
 252
 253 bool_t add_hook(uint32_t phase, hook_fn *fn, void *state)
 254 {
 255     struct phase_hook *h;
 256
 257     NEW(h);
 258     h->fn=fn;
 259     h->state=state;
 260     LIST_INSERT_HEAD(&hooks[phase],h,entry);
 261     return True;
 262 }
 263
 264 bool_t remove_hook(uint32_t phase, hook_fn *fn, void *state)
 265 {
 266     fatal("remove_hook: not implemented");
 267
 268     return False;
 269 }
 270
 271 void vslilog(struct log_if *lf, int priority, const char *message, va_list ap)
 272 {
 273     lf->vlogfn(lf->st,priority,message,ap);
 274 }
 275
 276 void slilog(struct log_if *lf, int priority, const char *message, ...)
 277 {
 278     va_list ap;
 279
 280     va_start(ap,message);
 281     vslilog(lf,priority,message,ap);
 282     va_end(ap);
 283 }
 284
 285 struct buffer {
 286     closure_t cl;
 287     struct buffer_if ops;
 288 };
 289
 290 void buffer_assert_free(struct buffer_if *buffer, cstring_t file,
 291                         int line)
 292 {
 293     if (!buffer->free) {
 294         fprintf(stderr,"secnet: BUF_ASSERT_FREE, %s line %d, owned by %s",
 295                 file,line,buffer->owner);
 296         assert(!"buffer_assert_free failure");
 297     }
 298 }
 299
 300 void buffer_assert_used(struct buffer_if *buffer, cstring_t file,
 301                         int line)
 302 {
 303     if (buffer->free) {
 304         fprintf(stderr,"secnet: BUF_ASSERT_USED, %s line %d, last owned by %s",
 305                 file,line,buffer->owner);
 306         assert(!"buffer_assert_used failure");
 307     }
 308 }
 309
 310 void buffer_init(struct buffer_if *buffer, int32_t max_start_pad)
 311 {
 312     assert(max_start_pad<=buffer->alloclen);
 313     buffer->start=buffer->base+max_start_pad;
 314     buffer->size=0;
 315 }
 316
 317 void buffer_destroy(struct buffer_if *buf)
 318 {
 319     BUF_ASSERT_FREE(buf);
 320     free(buf->base);
 321     buf->start=buf->base=0;
 322     buf->size=buf->alloclen=0;
 323 }
 324
 325 void *buf_append(struct buffer_if *buf, int32_t amount) {
 326     void *p;
 327     assert(amount <= buf_remaining_space(buf));
 328     p=buf->start + buf->size;
 329     buf->size+=amount;
 330     return p;
 331 }
 332
 333 void *buf_prepend(struct buffer_if *buf, int32_t amount) {
 334     assert(amount <= buf->start - buf->base);
 335     buf->size+=amount;
 336     return buf->start-=amount;
 337 }
 338
 339 void *buf_unappend(struct buffer_if *buf, int32_t amount) {
 340     if (buf->size < amount) return 0;
 341     return buf->start+(buf->size-=amount);
 342 }
 343
 344 void *buf_unprepend(struct buffer_if *buf, int32_t amount) {
 345     void *p;
 346     if (buf->size < amount) return 0;
 347     p=buf->start;
 348     buf->start+=amount;
 349     buf->size-=amount;
 350     return p;
 351 }
 352
 353 /* Append a two-byte length and the string to the buffer. Length is in
 354    network byte order. */
 355 void buf_append_string(struct buffer_if *buf, cstring_t s)
 356 {
 357     size_t len;
 358
 359     len=strlen(s);
 360     /* fixme: if string is longer than 65535, result is a corrupted packet */
 361     buf_append_uint16(buf,len);
 362     BUF_ADD_BYTES(append,buf,s,len);
 363 }
 364
 365 void buffer_new(struct buffer_if *buf, int32_t len)
 366 {
 367     buf->free=True;
 368     buf->owner=NULL;
 369     buf->flags=0;
 370     buf->loc.file=NULL;
 371     buf->loc.line=0;
 372     buf->size=0;
 373     buf->alloclen=len;
 374     buf->start=NULL;
 375     buf->base=safe_malloc(len,"buffer_new");
 376 }
 377
 378 void buffer_readonly_view(struct buffer_if *buf, const void *data, int32_t len)
 379 {
 380     buf->free=False;
 381     buf->owner="READONLY";
 382     buf->flags=0;
 383     buf->loc.file=NULL;
 384     buf->loc.line=0;
 385     buf->size=buf->alloclen=len;
 386     buf->base=buf->start=(uint8_t*)data;
 387 }
 388
 389 void buffer_readonly_clone(struct buffer_if *out, const struct buffer_if *in)
 390 {
 391     buffer_readonly_view(out,in->start,in->size);
 392 }
 393
 394 void buffer_copy(struct buffer_if *dst, const struct buffer_if *src)
 395 {
 396     if (dst->alloclen < src->alloclen) {
 397         dst->base=realloc(dst->base,src->alloclen);
 398         if (!dst->base) fatal_perror("buffer_copy");
 399         dst->alloclen = src->alloclen;
 400     }
 401     dst->start = dst->base + (src->start - src->base);
 402     dst->size = src->size;
 403     memcpy(dst->start, src->start, dst->size);
 404 }
 405
 406 static list_t *buffer_apply(closure_t *self, struct cloc loc, dict_t *context,
 407                             list_t *args)
 408 {
 409     struct buffer *st;
 410     item_t *item;
 411     dict_t *dict;
 412     bool_t lockdown=False;
 413     uint32_t len=DEFAULT_BUFFER_SIZE;
 414
 415     NEW(st);
 416     st->cl.description="buffer";
 417     st->cl.type=CL_BUFFER;
 418     st->cl.apply=NULL;
 419     st->cl.interface=&st->ops;
 420
 421     /* First argument, if present, is buffer length */
 422     item=list_elem(args,0);
 423     if (item) {
 424         if (item->type!=t_number) {
 425             cfgfatal(st->ops.loc,"buffer","first parameter must be a "
 426                      "number (buffer size)\n");
 427         }
 428         len=item->data.number;
 429         if (len<MIN_BUFFER_SIZE) {
 430             cfgfatal(st->ops.loc,"buffer","ludicrously small buffer size\n");
 431         }
 432         if (len>MAX_BUFFER_SIZE) {
 433             cfgfatal(st->ops.loc,"buffer","ludicrously large buffer size\n");
 434         }
 435     }
 436     /* Second argument, if present, is a dictionary */
 437     item=list_elem(args,1);
 438     if (item) {
 439         if (item->type!=t_dict) {
 440             cfgfatal(st->ops.loc,"buffer","second parameter must be a "
 441                      "dictionary\n");
 442         }
 443         dict=item->data.dict;
 444         lockdown=dict_read_bool(dict,"lockdown",False,"buffer",st->ops.loc,
 445                                 False);
 446     }
 447
 448     buffer_new(&st->ops,len);
 449     if (lockdown) {
 450         /* XXX mlock the buffer if possible */
 451     }
 452
 453     return new_closure(&st->cl);
 454 }
 455
 456 void send_nak(const struct comm_addr *dest, uint32_t our_index,
 457               uint32_t their_index, uint32_t msgtype,
 458               struct buffer_if *buf, const char *logwhy)
 459 {
 460     buffer_init(buf,calculate_max_start_pad());
 461     buf_append_uint32(buf,their_index);
 462     buf_append_uint32(buf,our_index);
 463     buf_append_uint32(buf,LABEL_NAK);
 464     if (logwhy)
 465         Message(M_INFO,"%s: %08"PRIx32"<-%08"PRIx32": %08"PRIx32":"
 466                 " %s; sending NAK\n",
 467                 comm_addr_to_string(dest),
 468                 our_index, their_index, msgtype, logwhy);
 469     dest->comm->sendmsg(dest->comm->st, buf, dest, 0);
 470 }
 471
 472 int consttime_memeq(const void *s1in, const void *s2in, size_t n)
 473 {
 474     const uint8_t *s1=s1in, *s2=s2in;
 475     register volatile uint8_t accumulator=0;
 476
 477     while (n-- > 0) {
 478         accumulator |= (*s1++ ^ *s2++);
 479     }
 480     accumulator |= accumulator >> 4; /* constant-time             */
 481     accumulator |= accumulator >> 2; /*  boolean canonicalisation */
 482     accumulator |= accumulator >> 1;
 483     accumulator &= 1;
 484     accumulator ^= 1;
 485     return accumulator;
 486 }
 487
 488 void util_module(dict_t *dict)
 489 {
 490     add_closure(dict,"sysbuffer",buffer_apply);
 491 }
 492
 493 void update_max_start_pad(int32_t *our_module_global, int32_t our_instance)
 494 {
 495     if (*our_module_global < our_instance)
 496         *our_module_global=our_instance;
 497 }
 498
 499 int32_t transform_max_start_pad, comm_max_start_pad;
 500
 501 int32_t calculate_max_start_pad(void)
 502 {
 503     return
 504         site_max_start_pad +
 505         transform_max_start_pad +
 506         comm_max_start_pad;
 507 }
 508
 509 void vslilog_part(struct log_if *lf, int priority, const char *message, va_list ap)
 510 {
 511     char *buff=lf->buff;
 512     size_t bp;
 513     char *nlp;
 514
 515     bp=strlen(buff);
 516     assert(bp < LOG_MESSAGE_BUFLEN);
 517     vsnprintf(buff+bp,LOG_MESSAGE_BUFLEN-bp,message,ap);
 518     buff[LOG_MESSAGE_BUFLEN-1] = '\n';
 519     buff[LOG_MESSAGE_BUFLEN] = '\0';
 520     /* Each line is sent separately */
 521     while ((nlp=strchr(buff,'\n'))) {
 522         *nlp=0;
 523         slilog(lf,priority,"%s",buff);
 524         memmove(buff,nlp+1,strlen(nlp+1)+1);
 525     }
 526 }
 527
 528 extern void slilog_part(struct log_if *lf, int priority, const char *message, ...)
 529 {
 530     va_list ap;
 531     va_start(ap,message);
 532     vslilog_part(lf,priority,message,ap);
 533     va_end(ap);
 534 }
 535
 536 void string_item_to_iaddr(const item_t *item, uint16_t port, union iaddr *ia,
 537                           const char *desc)
 538 {
 539 #ifndef CONFIG_IPV6
 540
 541     ia->sin.sin_family=AF_INET;
 542     ia->sin.sin_addr.s_addr=htonl(string_item_to_ipaddr(item,desc));
 543     ia->sin.sin_port=htons(port);
 544
 545 #else /* CONFIG_IPV6 => we have adns_text2addr */
 546
 547     if (item->type!=t_string)
 548         cfgfatal(item->loc,desc,"expecting a string IP (v4 or v6) address\n");
 549     socklen_t salen=sizeof(*ia);
 550     int r=adns_text2addr(item->data.string, port,
 551                          adns_qf_addrlit_ipv4_quadonly,
 552                          &ia->sa, &salen);
 553     assert(r!=ENOSPC);
 554     if (r) cfgfatal(item->loc,desc,"invalid IP (v4 or v6) address: %s\n",
 555                     strerror(r));
 556
 557 #endif /* CONFIG_IPV6 */
 558 }
 559
 560 #define IADDR_NBUFS 8
 561
 562 const char *iaddr_to_string(const union iaddr *ia)
 563 {
 564 #ifndef CONFIG_IPV6
 565
 566     SBUF_DEFINE(IADDR_NBUFS, 100);
 567
 568     assert(ia->sa.sa_family == AF_INET);
 569
 570     snprintf(SBUF, sizeof(SBUF), "[%s]:%d",
 571              inet_ntoa(ia->sin.sin_addr),
 572              ntohs(ia->sin.sin_port));
 573
 574 #else /* CONFIG_IPV6 => we have adns_addr2text */
 575
 576     SBUF_DEFINE(IADDR_NBUFS, 1+ADNS_ADDR2TEXT_BUFLEN+20);
 577
 578     int port;
 579
 580     char *addrbuf = SBUF;
 581     *addrbuf++ = '[';
 582     int addrbuflen = ADNS_ADDR2TEXT_BUFLEN;
 583
 584     int r = adns_addr2text(&ia->sa, 0, addrbuf, &addrbuflen, &port);
 585     if (r) {
 586         const char fmt[]= "scoped IPv6 addr, error: %.*s";
 587         sprintf(addrbuf, fmt,
 588                 (int)(ADNS_ADDR2TEXT_BUFLEN - sizeof(fmt)) /* underestimate */,
 589                 strerror(r));
 590     }
 591
 592     char *portbuf = addrbuf;
 593     int addrl = strlen(addrbuf);
 594     portbuf += addrl;
 595
 596     snprintf(portbuf, sizeof(SBUF)-addrl, "]:%d", port);
 597
 598 #endif /* CONFIG_IPV6 */
 599
 600     return SBUF;
 601 }
 602
 603 bool_t iaddr_equal(const union iaddr *ia, const union iaddr *ib,
 604                    bool_t ignoreport)
 605 {
 606     if (ia->sa.sa_family != ib->sa.sa_family)
 607         return 0;
 608     switch (ia->sa.sa_family) {
 609     case AF_INET:
 610         return ia->sin.sin_addr.s_addr == ib->sin.sin_addr.s_addr
 611            && (ignoreport ||
 612                ia->sin.sin_port        == ib->sin.sin_port);
 613 #ifdef CONFIG_IPV6
 614     case AF_INET6:
 615         return !memcmp(&ia->sin6.sin6_addr, &ib->sin6.sin6_addr, 16)
 616            &&  ia->sin6.sin6_scope_id  == ib->sin6.sin6_scope_id
 617            && (ignoreport ||
 618                ia->sin6.sin6_port      == ib->sin6.sin6_port)
 619             /* we ignore the flowinfo field */;
 620 #endif /* CONFIG_IPV6 */
 621     default:
 622         abort();
 623     }
 624 }
 625
 626 int iaddr_socklen(const union iaddr *ia)
 627 {
 628     switch (ia->sa.sa_family) {
 629     case AF_INET:  return sizeof(ia->sin);
 630 #ifdef CONFIG_IPV6
 631     case AF_INET6: return sizeof(ia->sin6);
 632 #endif /* CONFIG_IPV6 */
 633     default:       abort();
 634     }
 635 }
 636
 637 const char *pollbadbit(int revents)
 638 {
 639 #define BADBIT(b) \
 640     if ((revents & b)) return #b
 641     BADBIT(POLLERR);
 642     BADBIT(POLLHUP);
 643     /* POLLNVAL is handled by the event loop - see afterpoll_fn comment */
 644 #undef BADBIT
 645     return 0;
 646 }
 647
 648 enum async_linebuf_result
 649 async_linebuf_read(struct pollfd *pfd, struct buffer_if *buf,
 650                    const char **emsg_out)
 651 {
 652     int revents=pfd->revents;
 653
 654 #define BAD(m) do{ *emsg_out=(m); return async_linebuf_broken; }while(0)
 655
 656     const char *badbit=pollbadbit(revents);
 657     if (badbit) BAD(badbit);
 658
 659     if (!(revents & POLLIN))
 660         return async_linebuf_nothing;
 661
 662     /*
 663      * Data structure: A line which has been returned to the user is
 664      * stored in buf at base before start.  But we retain the usual
 665      * buffer meaning of size.  So:
 666      *
 667      *   | returned :    | input read,   |    unused    |
 668      *   |  to user : \0 |  awaiting     |     buffer   |
 669      *   |          :    |  processing   |      space   |
 670      *   |          :    |               |              |
 671      *   ^base           ^start          ^start+size    ^base+alloclen
 672      */
 673
 674     BUF_ASSERT_USED(buf);
 675
 676     /* firstly, eat any previous */
 677     if (buf->start != buf->base) {
 678         memmove(buf->base,buf->start,buf->size);
 679         buf->start=buf->base;
 680     }
 681
 682     uint8_t *searched=buf->base;
 683
 684     /*
 685      * During the workings here we do not use start.  We set start
 686      * when we return some actual data.  So we have this:
 687      *
 688      *   | searched     | read, might   |  unused      |
 689      *   |  for \n      |  contain \n   |   buffer     |
 690      *   |  none found  |  but not \0   |    space     |
 691      *   |              |               |              |
 692      *   ^base          ^searched       ^base+size     ^base+alloclen
 693      *  [^start]                        ^dataend
 694      *
 695      */
 696     for (;;) {
 697         uint8_t *dataend=buf->base+buf->size;
 698         char *newline=memchr(searched,'\n',dataend-searched);
 699         if (newline) {
 700             *newline=0;
 701             buf->start=newline+1;
 702             buf->size=dataend-buf->start;
 703             return async_linebuf_ok;
 704         }
 705         searched=dataend;
 706         ssize_t space=(buf->base+buf->alloclen)-dataend;
 707         if (!space) BAD("input line too long");
 708         ssize_t r=read(pfd->fd,searched,space);
 709         if (r==0) {
 710             *searched=0;
 711             *emsg_out=buf->size?"no newline at eof":0;
 712             buf->start=searched+1;
 713             buf->size=0;
 714             return async_linebuf_eof;
 715         }
 716         if (r<0) {
 717             if (errno==EINTR)
 718                 continue;
 719             if (iswouldblock(errno))
 720                 return async_linebuf_nothing;
 721             BAD(strerror(errno));
 722         }
 723         assert(r<=space);
 724         if (memchr(searched,0,r)) BAD("nul in input data");
 725         buf->size+=r;
 726     }
 727
 728 #undef BAD
 729 }