uipc_mbuf.c revision 21737
18837Sjkh/* 28837Sjkh * Copyright (c) 1982, 1986, 1988, 1991, 1993 38837Sjkh * The Regents of the University of California. All rights reserved. 48837Sjkh * 58837Sjkh * Redistribution and use in source and binary forms, with or without 68837Sjkh * modification, are permitted provided that the following conditions 712661Speter * are met: 88837Sjkh * 1. Redistributions of source code must retain the above copyright 98837Sjkh * notice, this list of conditions and the following disclaimer. 108837Sjkh * 2. Redistributions in binary form must reproduce the above copyright 118837Sjkh * notice, this list of conditions and the following disclaimer in the 128837Sjkh * documentation and/or other materials provided with the distribution. 138837Sjkh * 3. All advertising materials mentioning features or use of this software 148837Sjkh * must display the following acknowledgement: 158837Sjkh * This product includes software developed by the University of 168881Srgrimes * California, Berkeley and its contributors. 178881Srgrimes * 4. Neither the name of the University nor the names of its contributors 188837Sjkh * may be used to endorse or promote products derived from this software 198837Sjkh * without specific prior written permission. 208837Sjkh * 218837Sjkh * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 228837Sjkh * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 238837Sjkh * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 248837Sjkh * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 258837Sjkh * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 268837Sjkh * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 278837Sjkh * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 288837Sjkh * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 298837Sjkh * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 308837Sjkh * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 318837Sjkh * SUCH DAMAGE. 328837Sjkh * 338837Sjkh * @(#)uipc_mbuf.c 8.2 (Berkeley) 1/4/94 348837Sjkh * $FreeBSD: head/sys/kern/uipc_mbuf.c 21737 1997-01-15 20:46:02Z dg $ 358837Sjkh */ 368837Sjkh 378837Sjkh#include <sys/param.h> 388837Sjkh#include <sys/systm.h> 398837Sjkh#include <sys/proc.h> 408837Sjkh#include <sys/malloc.h> 418837Sjkh#define MBTYPES 428837Sjkh#include <sys/mbuf.h> 438837Sjkh#include <sys/kernel.h> 448791Sjkh#include <sys/syslog.h> 458791Sjkh#include <sys/domain.h> 468837Sjkh#include <sys/protosw.h> 478837Sjkh 488791Sjkh#include <vm/vm.h> 498791Sjkh#include <vm/vm_param.h> 508791Sjkh#include <vm/vm_kern.h> 518837Sjkh#include <vm/vm_extern.h> 528837Sjkh 538837Sjkhstatic void mbinit __P((void *)); 548837SjkhSYSINIT(mbuf, SI_SUB_MBUF, SI_ORDER_FIRST, mbinit, NULL) 558837Sjkh 568860Sjkhstruct mbuf *mbutl; 578860Sjkhchar *mclrefcnt; 588837Sjkhstruct mbstat mbstat; 598837Sjkhstruct mbuf *mmbfree; 608837Sjkhunion mcluster *mclfree; 6112661Speterint max_linkhdr; 629202Srgrimesint max_protohdr; 638860Sjkhint max_hdr; 6412661Speterint max_datalen; 658837Sjkh 668837Sjkhstatic void m_reclaim __P((void)); 6712661Speter 6812661Speter/* "number of clusters of pages" */ 6912661Speter#define NCL_INIT 1 7012661Speter 7112661Speter#define NMB_INIT 16 7212661Speter 7312661Speter/* ARGSUSED*/ 748837Sjkhstatic void 758837Sjkhmbinit(dummy) 768837Sjkh void *dummy; 7712661Speter{ 788837Sjkh int s; 798837Sjkh 808837Sjkh mmbfree = NULL; mclfree = NULL; 818837Sjkh s = splimp(); 8212661Speter if (m_mballoc(NMB_INIT, M_DONTWAIT) == 0) 838837Sjkh goto bad; 8412661Speter if (m_clalloc(NCL_INIT, M_DONTWAIT) == 0) 858837Sjkh goto bad; 8612661Speter splx(s); 8712661Speter return; 8812661Speterbad: 899202Srgrimes panic("mbinit"); 9012661Speter} 9112661Speter 9212661Speter/* 9312661Speter * Allocate at least nmb mbufs and place on mbuf free list. 9412661Speter * Must be called at splimp. 9512661Speter */ 9612661Speter/* ARGSUSED */ 978837Sjkhint 988837Sjkhm_mballoc(nmb, nowait) 998837Sjkh register int nmb; 1008837Sjkh int nowait; 1018837Sjkh{ 1028837Sjkh register caddr_t p; 10312661Speter register int i; 1048860Sjkh int nbytes; 1058837Sjkh 1068837Sjkh /* Once we run out of map space, it will be impossible to get 10712661Speter * any more (nothing is ever freed back to the map) (XXX which 10812661Speter * is dumb). (however you are not dead as m_reclaim might 10912661Speter * still be able to free a substantial amount of space). 11012661Speter */ 11112661Speter if (mb_map_full) 11212661Speter return (0); 11312661Speter 1148837Sjkh nbytes = round_page(nmb * MSIZE); 1158837Sjkh p = (caddr_t)kmem_malloc(mb_map, nbytes, nowait ? M_NOWAIT : M_WAITOK); 1168837Sjkh /* 117 * Either the map is now full, or this is nowait and there 118 * are no pages left. 119 */ 120 if (p == NULL) 121 return (0); 122 123 nmb = nbytes / MSIZE; 124 for (i = 0; i < nmb; i++) { 125 ((struct mbuf *)p)->m_next = mmbfree; 126 mmbfree = (struct mbuf *)p; 127 p += MSIZE; 128 } 129 mbstat.m_mbufs += nmb; 130 return (1); 131} 132 133/* 134 * Allocate some number of mbuf clusters 135 * and place on cluster free list. 136 * Must be called at splimp. 137 */ 138/* ARGSUSED */ 139int 140m_clalloc(ncl, nowait) 141 register int ncl; 142 int nowait; 143{ 144 register caddr_t p; 145 register int i; 146 int npg; 147 148 /* 149 * Once we run out of map space, it will be impossible 150 * to get any more (nothing is ever freed back to the 151 * map). 152 */ 153 if (mb_map_full) 154 return (0); 155 156 npg = ncl; 157 p = (caddr_t)kmem_malloc(mb_map, ctob(npg), 158 nowait ? M_NOWAIT : M_WAITOK); 159 /* 160 * Either the map is now full, or this is nowait and there 161 * are no pages left. 162 */ 163 if (p == NULL) 164 return (0); 165 166 ncl = ncl * PAGE_SIZE / MCLBYTES; 167 for (i = 0; i < ncl; i++) { 168 ((union mcluster *)p)->mcl_next = mclfree; 169 mclfree = (union mcluster *)p; 170 p += MCLBYTES; 171 mbstat.m_clfree++; 172 } 173 mbstat.m_clusters += ncl; 174 return (1); 175} 176 177/* 178 * When MGET failes, ask protocols to free space when short of memory, 179 * then re-attempt to allocate an mbuf. 180 */ 181struct mbuf * 182m_retry(i, t) 183 int i, t; 184{ 185 register struct mbuf *m; 186 187 m_reclaim(); 188#define m_retry(i, t) (struct mbuf *)0 189 MGET(m, i, t); 190#undef m_retry 191 if (m != NULL) 192 mbstat.m_wait++; 193 else 194 mbstat.m_drops++; 195 return (m); 196} 197 198/* 199 * As above; retry an MGETHDR. 200 */ 201struct mbuf * 202m_retryhdr(i, t) 203 int i, t; 204{ 205 register struct mbuf *m; 206 207 m_reclaim(); 208#define m_retryhdr(i, t) (struct mbuf *)0 209 MGETHDR(m, i, t); 210#undef m_retryhdr 211 if (m != NULL) 212 mbstat.m_wait++; 213 else 214 mbstat.m_drops++; 215 return (m); 216} 217 218static void 219m_reclaim() 220{ 221 register struct domain *dp; 222 register struct protosw *pr; 223 int s = splimp(); 224 225 for (dp = domains; dp; dp = dp->dom_next) 226 for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++) 227 if (pr->pr_drain) 228 (*pr->pr_drain)(); 229 splx(s); 230 mbstat.m_drain++; 231} 232 233/* 234 * Space allocation routines. 235 * These are also available as macros 236 * for critical paths. 237 */ 238struct mbuf * 239m_get(nowait, type) 240 int nowait, type; 241{ 242 register struct mbuf *m; 243 244 MGET(m, nowait, type); 245 return (m); 246} 247 248struct mbuf * 249m_gethdr(nowait, type) 250 int nowait, type; 251{ 252 register struct mbuf *m; 253 254 MGETHDR(m, nowait, type); 255 return (m); 256} 257 258struct mbuf * 259m_getclr(nowait, type) 260 int nowait, type; 261{ 262 register struct mbuf *m; 263 264 MGET(m, nowait, type); 265 if (m == 0) 266 return (0); 267 bzero(mtod(m, caddr_t), MLEN); 268 return (m); 269} 270 271struct mbuf * 272m_free(m) 273 struct mbuf *m; 274{ 275 register struct mbuf *n; 276 277 MFREE(m, n); 278 return (n); 279} 280 281void 282m_freem(m) 283 register struct mbuf *m; 284{ 285 register struct mbuf *n; 286 287 if (m == NULL) 288 return; 289 do { 290 MFREE(m, n); 291 m = n; 292 } while (m); 293} 294 295/* 296 * Mbuffer utility routines. 297 */ 298 299/* 300 * Lesser-used path for M_PREPEND: 301 * allocate new mbuf to prepend to chain, 302 * copy junk along. 303 */ 304struct mbuf * 305m_prepend(m, len, how) 306 register struct mbuf *m; 307 int len, how; 308{ 309 struct mbuf *mn; 310 311 MGET(mn, how, m->m_type); 312 if (mn == (struct mbuf *)NULL) { 313 m_freem(m); 314 return ((struct mbuf *)NULL); 315 } 316 if (m->m_flags & M_PKTHDR) { 317 M_COPY_PKTHDR(mn, m); 318 m->m_flags &= ~M_PKTHDR; 319 } 320 mn->m_next = m; 321 m = mn; 322 if (len < MHLEN) 323 MH_ALIGN(m, len); 324 m->m_len = len; 325 return (m); 326} 327 328/* 329 * Make a copy of an mbuf chain starting "off0" bytes from the beginning, 330 * continuing for "len" bytes. If len is M_COPYALL, copy to end of mbuf. 331 * The wait parameter is a choice of M_WAIT/M_DONTWAIT from caller. 332 */ 333static int MCFail; 334 335struct mbuf * 336m_copym(m, off0, len, wait) 337 register struct mbuf *m; 338 int off0, wait; 339 register int len; 340{ 341 register struct mbuf *n, **np; 342 register int off = off0; 343 struct mbuf *top; 344 int copyhdr = 0; 345 346 if (off < 0 || len < 0) 347 panic("m_copym"); 348 if (off == 0 && m->m_flags & M_PKTHDR) 349 copyhdr = 1; 350 while (off > 0) { 351 if (m == 0) 352 panic("m_copym"); 353 if (off < m->m_len) 354 break; 355 off -= m->m_len; 356 m = m->m_next; 357 } 358 np = ⊤ 359 top = 0; 360 while (len > 0) { 361 if (m == 0) { 362 if (len != M_COPYALL) 363 panic("m_copym"); 364 break; 365 } 366 MGET(n, wait, m->m_type); 367 *np = n; 368 if (n == 0) 369 goto nospace; 370 if (copyhdr) { 371 M_COPY_PKTHDR(n, m); 372 if (len == M_COPYALL) 373 n->m_pkthdr.len -= off0; 374 else 375 n->m_pkthdr.len = len; 376 copyhdr = 0; 377 } 378 n->m_len = min(len, m->m_len - off); 379 if (m->m_flags & M_EXT) { 380 n->m_data = m->m_data + off; 381 if(!m->m_ext.ext_ref) 382 mclrefcnt[mtocl(m->m_ext.ext_buf)]++; 383 else 384 (*(m->m_ext.ext_ref))(m->m_ext.ext_buf, 385 m->m_ext.ext_size); 386 n->m_ext = m->m_ext; 387 n->m_flags |= M_EXT; 388 } else 389 bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t), 390 (unsigned)n->m_len); 391 if (len != M_COPYALL) 392 len -= n->m_len; 393 off = 0; 394 m = m->m_next; 395 np = &n->m_next; 396 } 397 if (top == 0) 398 MCFail++; 399 return (top); 400nospace: 401 m_freem(top); 402 MCFail++; 403 return (0); 404} 405 406/* 407 * Copy an entire packet, including header (which must be present). 408 * An optimization of the common case `m_copym(m, 0, M_COPYALL, how)'. 409 */ 410struct mbuf * 411m_copypacket(m, how) 412 struct mbuf *m; 413 int how; 414{ 415 struct mbuf *top, *n, *o; 416 417 MGET(n, how, m->m_type); 418 top = n; 419 if (!n) 420 goto nospace; 421 422 M_COPY_PKTHDR(n, m); 423 n->m_len = m->m_len; 424 if (m->m_flags & M_EXT) { 425 n->m_data = m->m_data; 426 mclrefcnt[mtocl(m->m_ext.ext_buf)]++; 427 n->m_ext = m->m_ext; 428 n->m_flags |= M_EXT; 429 } else { 430 bcopy(mtod(m, char *), mtod(n, char *), n->m_len); 431 } 432 433 m = m->m_next; 434 while (m) { 435 MGET(o, how, m->m_type); 436 if (!o) 437 goto nospace; 438 439 n->m_next = o; 440 n = n->m_next; 441 442 n->m_len = m->m_len; 443 if (m->m_flags & M_EXT) { 444 n->m_data = m->m_data; 445 mclrefcnt[mtocl(m->m_ext.ext_buf)]++; 446 n->m_ext = m->m_ext; 447 n->m_flags |= M_EXT; 448 } else { 449 bcopy(mtod(m, char *), mtod(n, char *), n->m_len); 450 } 451 452 m = m->m_next; 453 } 454 return top; 455nospace: 456 m_freem(top); 457 MCFail++; 458 return 0; 459} 460 461/* 462 * Copy data from an mbuf chain starting "off" bytes from the beginning, 463 * continuing for "len" bytes, into the indicated buffer. 464 */ 465void 466m_copydata(m, off, len, cp) 467 register struct mbuf *m; 468 register int off; 469 register int len; 470 caddr_t cp; 471{ 472 register unsigned count; 473 474 if (off < 0 || len < 0) 475 panic("m_copydata"); 476 while (off > 0) { 477 if (m == 0) 478 panic("m_copydata"); 479 if (off < m->m_len) 480 break; 481 off -= m->m_len; 482 m = m->m_next; 483 } 484 while (len > 0) { 485 if (m == 0) 486 panic("m_copydata"); 487 count = min(m->m_len - off, len); 488 bcopy(mtod(m, caddr_t) + off, cp, count); 489 len -= count; 490 cp += count; 491 off = 0; 492 m = m->m_next; 493 } 494} 495 496/* 497 * Concatenate mbuf chain n to m. 498 * Both chains must be of the same type (e.g. MT_DATA). 499 * Any m_pkthdr is not updated. 500 */ 501void 502m_cat(m, n) 503 register struct mbuf *m, *n; 504{ 505 while (m->m_next) 506 m = m->m_next; 507 while (n) { 508 if (m->m_flags & M_EXT || 509 m->m_data + m->m_len + n->m_len >= &m->m_dat[MLEN]) { 510 /* just join the two chains */ 511 m->m_next = n; 512 return; 513 } 514 /* splat the data from one into the other */ 515 bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len, 516 (u_int)n->m_len); 517 m->m_len += n->m_len; 518 n = m_free(n); 519 } 520} 521 522void 523m_adj(mp, req_len) 524 struct mbuf *mp; 525 int req_len; 526{ 527 register int len = req_len; 528 register struct mbuf *m; 529 register count; 530 531 if ((m = mp) == NULL) 532 return; 533 if (len >= 0) { 534 /* 535 * Trim from head. 536 */ 537 while (m != NULL && len > 0) { 538 if (m->m_len <= len) { 539 len -= m->m_len; 540 m->m_len = 0; 541 m = m->m_next; 542 } else { 543 m->m_len -= len; 544 m->m_data += len; 545 len = 0; 546 } 547 } 548 m = mp; 549 if (mp->m_flags & M_PKTHDR) 550 m->m_pkthdr.len -= (req_len - len); 551 } else { 552 /* 553 * Trim from tail. Scan the mbuf chain, 554 * calculating its length and finding the last mbuf. 555 * If the adjustment only affects this mbuf, then just 556 * adjust and return. Otherwise, rescan and truncate 557 * after the remaining size. 558 */ 559 len = -len; 560 count = 0; 561 for (;;) { 562 count += m->m_len; 563 if (m->m_next == (struct mbuf *)0) 564 break; 565 m = m->m_next; 566 } 567 if (m->m_len >= len) { 568 m->m_len -= len; 569 if (mp->m_flags & M_PKTHDR) 570 mp->m_pkthdr.len -= len; 571 return; 572 } 573 count -= len; 574 if (count < 0) 575 count = 0; 576 /* 577 * Correct length for chain is "count". 578 * Find the mbuf with last data, adjust its length, 579 * and toss data from remaining mbufs on chain. 580 */ 581 m = mp; 582 if (m->m_flags & M_PKTHDR) 583 m->m_pkthdr.len = count; 584 for (; m; m = m->m_next) { 585 if (m->m_len >= count) { 586 m->m_len = count; 587 break; 588 } 589 count -= m->m_len; 590 } 591 while (m->m_next) 592 (m = m->m_next) ->m_len = 0; 593 } 594} 595 596/* 597 * Rearange an mbuf chain so that len bytes are contiguous 598 * and in the data area of an mbuf (so that mtod and dtom 599 * will work for a structure of size len). Returns the resulting 600 * mbuf chain on success, frees it and returns null on failure. 601 * If there is room, it will add up to max_protohdr-len extra bytes to the 602 * contiguous region in an attempt to avoid being called next time. 603 */ 604static int MPFail; 605 606struct mbuf * 607m_pullup(n, len) 608 register struct mbuf *n; 609 int len; 610{ 611 register struct mbuf *m; 612 register int count; 613 int space; 614 615 /* 616 * If first mbuf has no cluster, and has room for len bytes 617 * without shifting current data, pullup into it, 618 * otherwise allocate a new mbuf to prepend to the chain. 619 */ 620 if ((n->m_flags & M_EXT) == 0 && 621 n->m_data + len < &n->m_dat[MLEN] && n->m_next) { 622 if (n->m_len >= len) 623 return (n); 624 m = n; 625 n = n->m_next; 626 len -= m->m_len; 627 } else { 628 if (len > MHLEN) 629 goto bad; 630 MGET(m, M_DONTWAIT, n->m_type); 631 if (m == 0) 632 goto bad; 633 m->m_len = 0; 634 if (n->m_flags & M_PKTHDR) { 635 M_COPY_PKTHDR(m, n); 636 n->m_flags &= ~M_PKTHDR; 637 } 638 } 639 space = &m->m_dat[MLEN] - (m->m_data + m->m_len); 640 do { 641 count = min(min(max(len, max_protohdr), space), n->m_len); 642 bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len, 643 (unsigned)count); 644 len -= count; 645 m->m_len += count; 646 n->m_len -= count; 647 space -= count; 648 if (n->m_len) 649 n->m_data += count; 650 else 651 n = m_free(n); 652 } while (len > 0 && n); 653 if (len > 0) { 654 (void) m_free(m); 655 goto bad; 656 } 657 m->m_next = n; 658 return (m); 659bad: 660 m_freem(n); 661 MPFail++; 662 return (0); 663} 664 665/* 666 * Partition an mbuf chain in two pieces, returning the tail -- 667 * all but the first len0 bytes. In case of failure, it returns NULL and 668 * attempts to restore the chain to its original state. 669 */ 670struct mbuf * 671m_split(m0, len0, wait) 672 register struct mbuf *m0; 673 int len0, wait; 674{ 675 register struct mbuf *m, *n; 676 unsigned len = len0, remain; 677 678 for (m = m0; m && len > m->m_len; m = m->m_next) 679 len -= m->m_len; 680 if (m == 0) 681 return (0); 682 remain = m->m_len - len; 683 if (m0->m_flags & M_PKTHDR) { 684 MGETHDR(n, wait, m0->m_type); 685 if (n == 0) 686 return (0); 687 n->m_pkthdr.rcvif = m0->m_pkthdr.rcvif; 688 n->m_pkthdr.len = m0->m_pkthdr.len - len0; 689 m0->m_pkthdr.len = len0; 690 if (m->m_flags & M_EXT) 691 goto extpacket; 692 if (remain > MHLEN) { 693 /* m can't be the lead packet */ 694 MH_ALIGN(n, 0); 695 n->m_next = m_split(m, len, wait); 696 if (n->m_next == 0) { 697 (void) m_free(n); 698 return (0); 699 } else 700 return (n); 701 } else 702 MH_ALIGN(n, remain); 703 } else if (remain == 0) { 704 n = m->m_next; 705 m->m_next = 0; 706 return (n); 707 } else { 708 MGET(n, wait, m->m_type); 709 if (n == 0) 710 return (0); 711 M_ALIGN(n, remain); 712 } 713extpacket: 714 if (m->m_flags & M_EXT) { 715 n->m_flags |= M_EXT; 716 n->m_ext = m->m_ext; 717 if(!m->m_ext.ext_ref) 718 mclrefcnt[mtocl(m->m_ext.ext_buf)]++; 719 else 720 (*(m->m_ext.ext_ref))(m->m_ext.ext_buf, 721 m->m_ext.ext_size); 722 m->m_ext.ext_size = 0; /* For Accounting XXXXXX danger */ 723 n->m_data = m->m_data + len; 724 } else { 725 bcopy(mtod(m, caddr_t) + len, mtod(n, caddr_t), remain); 726 } 727 n->m_len = remain; 728 m->m_len = len; 729 n->m_next = m->m_next; 730 m->m_next = 0; 731 return (n); 732} 733/* 734 * Routine to copy from device local memory into mbufs. 735 */ 736struct mbuf * 737m_devget(buf, totlen, off0, ifp, copy) 738 char *buf; 739 int totlen, off0; 740 struct ifnet *ifp; 741 void (*copy) __P((char *from, caddr_t to, u_int len)); 742{ 743 register struct mbuf *m; 744 struct mbuf *top = 0, **mp = ⊤ 745 register int off = off0, len; 746 register char *cp; 747 char *epkt; 748 749 cp = buf; 750 epkt = cp + totlen; 751 if (off) { 752 cp += off + 2 * sizeof(u_short); 753 totlen -= 2 * sizeof(u_short); 754 } 755 MGETHDR(m, M_DONTWAIT, MT_DATA); 756 if (m == 0) 757 return (0); 758 m->m_pkthdr.rcvif = ifp; 759 m->m_pkthdr.len = totlen; 760 m->m_len = MHLEN; 761 762 while (totlen > 0) { 763 if (top) { 764 MGET(m, M_DONTWAIT, MT_DATA); 765 if (m == 0) { 766 m_freem(top); 767 return (0); 768 } 769 m->m_len = MLEN; 770 } 771 len = min(totlen, epkt - cp); 772 if (len >= MINCLSIZE) { 773 MCLGET(m, M_DONTWAIT); 774 if (m->m_flags & M_EXT) 775 m->m_len = len = min(len, MCLBYTES); 776 else 777 len = m->m_len; 778 } else { 779 /* 780 * Place initial small packet/header at end of mbuf. 781 */ 782 if (len < m->m_len) { 783 if (top == 0 && len + max_linkhdr <= m->m_len) 784 m->m_data += max_linkhdr; 785 m->m_len = len; 786 } else 787 len = m->m_len; 788 } 789 if (copy) 790 copy(cp, mtod(m, caddr_t), (unsigned)len); 791 else 792 bcopy(cp, mtod(m, caddr_t), (unsigned)len); 793 cp += len; 794 *mp = m; 795 mp = &m->m_next; 796 totlen -= len; 797 if (cp == epkt) 798 cp = buf; 799 } 800 return (top); 801} 802 803/* 804 * Copy data from a buffer back into the indicated mbuf chain, 805 * starting "off" bytes from the beginning, extending the mbuf 806 * chain if necessary. 807 */ 808void 809m_copyback(m0, off, len, cp) 810 struct mbuf *m0; 811 register int off; 812 register int len; 813 caddr_t cp; 814{ 815 register int mlen; 816 register struct mbuf *m = m0, *n; 817 int totlen = 0; 818 819 if (m0 == 0) 820 return; 821 while (off > (mlen = m->m_len)) { 822 off -= mlen; 823 totlen += mlen; 824 if (m->m_next == 0) { 825 n = m_getclr(M_DONTWAIT, m->m_type); 826 if (n == 0) 827 goto out; 828 n->m_len = min(MLEN, len + off); 829 m->m_next = n; 830 } 831 m = m->m_next; 832 } 833 while (len > 0) { 834 mlen = min (m->m_len - off, len); 835 bcopy(cp, off + mtod(m, caddr_t), (unsigned)mlen); 836 cp += mlen; 837 len -= mlen; 838 mlen += off; 839 off = 0; 840 totlen += mlen; 841 if (len == 0) 842 break; 843 if (m->m_next == 0) { 844 n = m_get(M_DONTWAIT, m->m_type); 845 if (n == 0) 846 break; 847 n->m_len = min(MLEN, len); 848 m->m_next = n; 849 } 850 m = m->m_next; 851 } 852out: if (((m = m0)->m_flags & M_PKTHDR) && (m->m_pkthdr.len < totlen)) 853 m->m_pkthdr.len = totlen; 854} 855