1.\" $NetBSD: mbuf.9,v 1.40 2005/08/23 09:34:11 yamt Exp $ 2.\" 3.\" Copyright (c) 1997 The NetBSD Foundation, Inc. 4.\" All rights reserved. 5.\" 6.\" This documentation is derived from text contributed to The NetBSD Foundation 7.\" by S.P.Zeidler (aka stargazer). 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 3. All advertising materials mentioning features or use of this software 18.\" must display the following acknowledgement: 19.\" This product includes software developed by the NetBSD 20.\" Foundation, Inc. and its contributors. 21.\" 4. Neither the name of The NetBSD Foundation nor the names of its 22.\" contributors may be used to endorse or promote products derived 23.\" from this software without specific prior written permission. 24.\" 25.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 26.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 27.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 28.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 29.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 30.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 31.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 32.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 33.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 34.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 35.\" POSSIBILITY OF SUCH DAMAGE. 36.\" 37.Dd August 23, 2005 38.Dt MBUF 9 39.Os 40.Sh NAME 41.Nm mbuf , 42.Nm m_get , 43.Nm m_getclr , 44.Nm m_gethdr , 45.Nm m_devget , 46.Nm m_copym , 47.Nm m_copypacket , 48.Nm m_copydata , 49.Nm m_copyback , 50.Nm m_copyback_cow , 51.Nm m_cat , 52.Nm m_dup , 53.Nm m_makewritable , 54.Nm m_prepend , 55.Nm m_pulldown , 56.Nm m_pullup , 57.Nm m_split , 58.Nm m_adj , 59.Nm m_apply , 60.Nm m_free , 61.Nm m_freem , 62.Nm mtod , 63.Nm MGET , 64.Nm MGETHDR , 65.Nm MEXTMALLOC , 66.Nm MEXTADD , 67.Nm MCLGET , 68.Nm M_COPY_PKTHDR , 69.Nm M_MOVE_PKTHDR , 70.Nm M_ALIGN , 71.Nm MH_ALIGN , 72.Nm M_LEADINGSPACE , 73.Nm M_TRAILINGSPACE , 74.Nm M_PREPEND , 75.Nm MCHTYPE , 76.Nm MEXTREMOVE , 77.Nm MFREE , 78.Nd "functions and macros for managing memory used by networking code" 79.Sh SYNOPSIS 80.In sys/mbuf.h 81.Ft struct mbuf * 82.Fn m_get "int nowait" "int type" 83.Ft struct mbuf * 84.Fn m_getclr "int nowait" "int type" 85.Ft struct mbuf * 86.Fn m_gethdr "int nowait" "int type" 87.Ft struct mbuf * 88.Fn m_devget "char *buf" "int totlen" "int off0" "struct ifnet *ifp" "void (*copy)(const void *, void *, size_t)" 89.Ft struct mbuf * 90.Fn m_copym "struct mbuf *m" "int off0" "int len" "int wait" 91.Ft struct mbuf * 92.Fn m_copypacket "struct mbuf *m" "int how" 93.Ft void 94.Fn m_copydata "struct mbuf *m" "int off" "int len" "caddr_t cp" 95.Ft void 96.Fn m_copyback "struct mbuf *m0" "int off" "int len" "caddr_t cp" 97.Ft struct mbuf * 98.Fn m_copyback_cow "struct mbuf *m0" "int off" "int len" "caddr_t cp" "int how" 99.Ft int 100.Fn m_makewritable "struct mbuf **mp" "int off" "int len" "int how" 101.Ft void 102.Fn m_cat "struct mbuf *m" "struct mbuf *n" 103.Ft struct mbuf * 104.Fn m_dup "struct mbuf *m" "int off0" "int len" "int wait" 105.Ft struct mbuf * 106.Fn m_prepend "struct mbuf *m" "int len" "int how" 107.Ft struct mbuf * 108.Fn m_pulldown "struct mbuf *m" "int off" "int len" "int *offp" 109.Ft struct mbuf * 110.Fn m_pullup "struct mbuf *n" "int len" 111.Ft struct mbuf * 112.Fn m_split "struct mbuf *m0" "int len0" "int wait" 113.Ft void 114.Fn m_adj "struct mbuf *mp" "int req_len" 115.Ft int 116.Fn m_apply "struct mbuf *m" "int off" "int len" "int *f(void *, caddr_t, unsigned int)" "void *arg" 117.Ft struct mbuf * 118.Fn m_free "struct mbuf *m" 119.Ft void 120.Fn m_freem "struct mbuf *m" 121.Ft datatype 122.Fn mtod "struct mbuf *m" "datatype" 123.Ft void 124.Fn MGET "struct mbuf *m" "int how" "int type" 125.Ft void 126.Fn MGETHDR "struct mbuf *m" "int how" "int type" 127.Ft void 128.Fn MEXTMALLOC "struct mbuf *m" "int len" "int how" 129.Ft void 130.Fn MEXTADD "struct mbuf *m" "caddr_t buf" "int size" "int type" "void (*free)(struct mbuf *, caddr_t, size_t, void *)" "void *arg" 131.Ft void 132.Fn MCLGET "struct mbuf *m" "int how" 133.Ft void 134.Fn M_COPY_PKTHDR "struct mbuf *to" "struct mbuf *from" 135.Ft void 136.Fn M_MOVE_PKTHDR "struct mbuf *to" "struct mbuf *from" 137.Ft void 138.Fn M_ALIGN "struct mbuf *m" "int len" 139.Ft void 140.Fn MH_ALIGN "struct mbuf *m" "int len" 141.Ft int 142.Fn M_LEADINGSPACE "struct mbuf *m" 143.Ft int 144.Fn M_TRAILINGSPACE "struct mbuf *m" 145.Ft void 146.Fn M_PREPEND "struct mbuf *m" "int plen" "int how" 147.Ft void 148.Fn MCHTYPE "struct mbuf *m" "int type" 149.Ft void 150.Fn MEXTREMOVE "struct mbuf *m" 151.Ft void 152.Fn MFREE "struct mbuf *m" "struct mbuf *n" 153.Sh DESCRIPTION 154The 155.Nm 156functions and macros provide an easy and consistent way to handle 157a networking stack's memory management needs. 158An 159.Nm 160consists of a header and a data area. 161It is of a fixed size, 162.Dv MSIZE 163.Pq defined in Aq Pa machine/param.h , 164which includes overhead. 165The header contains a pointer to the next 166.Nm 167in the 168.Sq "mbuf chain" , 169a pointer to the next 170.Sq "mbuf chain" , 171a pointer to the data area, the amount of data in this mbuf, its type 172and a 173.Dv flags 174field. 175.Pp 176The 177.Dv type 178variable can signify: 179.Bl -tag -compact -offset indent -width "XXXXXXXXXXX" 180.It Dv MT_FREE 181the mbuf should be on the ``free'' list 182.It Dv MT_DATA 183data was dynamically allocated 184.It Dv MT_HEADER 185data is a packet header 186.It Dv MT_SONAME 187data is a socket name 188.It Dv MT_SOOPTS 189data is socket options 190.It Dv MT_FTABLE 191data is the fragment reassembly header 192.It Dv MT_CONTROL 193mbuf contains ancillary \&(protocol control\&) data 194.It Dv MT_OOBDATA 195mbuf contains out-of-band data. 196.El 197.Pp 198The 199.Dv flags 200variable contains information describing the 201.Nm , 202notably: 203.Bl -tag -compact -offset indent -width "XXXXXXXXXXX" 204.It Dv M_EXT 205has external storage 206.It Dv M_PKTHDR 207is start of record 208.It Dv M_EOR 209is end of record 210.It Dv M_CLUSTER 211external storage is a cluster. 212.El 213.Pp 214If an 215.Nm 216designates the start of a record 217.Pq Dv M_PKTHDR , 218its 219.Dv flags 220field may contain additional information describing the content of 221the record: 222.Bl -tag -compact -offset indent -width "XXXXXXXXXXX" 223.It Dv M_BCAST 224sent/received as link-level broadcast 225.It Dv M_MCAST 226sent/received as link-level multicast 227.It Dv M_LINK0 , 228.It Dv M_LINK1 , 229.It Dv M_LINK2 230three link-level specific flags. 231.El 232.Pp 233An 234.Nm 235may add a single 236.Sq "mbuf cluster" 237of 238.Dv MCLBYTES 239bytes 240.Pq also defined in Aq Pa machine/param.h , 241which has no additional overhead 242and is used instead of the internal data area; this is done when at least 243.Dv MINCLSIZE 244bytes of data must be stored. 245.Pp 246When the 247.Dv M_EXT 248flag is raised for an mbuf, 249the external storage area could be shared among multiple mbufs. 250Be careful when you attempt to overwrite the data content of the mbuf. 251.Bl -tag -width compact 252.It Fn m_get "int nowait" "int type" 253Allocates an mbuf and initializes it to contain internal data. 254The 255.Fa nowait 256parameter is a choice of 257.Dv M_WAIT / M_DONTWAIT 258from caller. 259.Dv M_WAIT 260means the call cannot fail, but may take forever. 261The 262.Fa type 263parameter is an mbuf type. 264.It Fn m_getclr "int nowait" "int type" 265Allocates an mbuf and initializes it to contain internal data, then 266zeros the data area. 267The 268.Fa nowait 269parameter is a choice of 270.Dv M_WAIT / M_DONTWAIT 271from caller. 272The 273.Fa type 274parameter is an mbuf type. 275.It Fn m_gethdr "int nowait" "int type" 276Allocates an mbuf and initializes it to contain a packet header and internal 277data. 278The 279.Fa nowait 280parameter is a choice of 281.Dv M_WAIT / M_DONTWAIT 282from caller. 283The 284.Fa type 285parameter is an mbuf type. 286.It Fn m_devget "char *buf" "int totlen" "int off0" "struct ifnet *ifp" "void (*copy)(const void *, void *, size_t)" 287Copies 288.Fa len 289bytes from device local memory into mbufs using copy routine 290.Fa copy . 291If parameter 292.Fa off 293is non-zero, the packet is supposed to be trailer-encapsulated and 294.Fa off 295bytes plus the type and length fields will be skipped before copying. 296Returns the top of the mbuf chain it created. 297.It Fn m_copym "struct mbuf *m" "int off0" "int len" "int wait" 298Creates a copy of an mbuf chain starting 299.Fa off0 300bytes from the beginning, continuing for 301.Fa len 302bytes. 303If the 304.Fa len 305requested is 306.Dv M_COPYALL , 307the complete mbuf chain will be copied. 308The 309.Fa wait 310parameter is a choice of 311.Dv M_WAIT / M_DONTWAIT 312from caller. 313.It Fn m_copypacket "struct mbuf *m" "int how" 314Copies an entire packet, including header (which must be present). 315This function is an optimization of the common case 316.Li m_copym(m, 0, Dv M_COPYALL, Fa how ) . 317.It Fn m_copydata "struct mbuf *m" "int off" "int len" "caddr_t cp" 318Copies 319.Fa len 320bytes data from mbuf chain 321.Fa m 322into the buffer 323.Fa cp , 324starting 325.Fa off 326bytes from the beginning. 327.It Fn m_copyback "struct mbuf *m0" "int off" "int len" "caddr_t cp" 328Copies 329.Fa len 330bytes data from buffer 331.Fa cp 332back into the mbuf chain 333.Fa m0 , 334starting 335.Fa off 336bytes from the beginning of the chain, extending the mbuf chain if necessary. 337.Fn m_copyback 338can only fail when extending the chain. 339The caller should check for this kind of failure 340by checking the resulting length of the chain in that case. 341It is an error to use 342.Fn m_copyback 343on read-only mbufs. 344.It Fn m_copyback_cow "struct mbuf *m0" "int off" "int len" "caddr_t cp" \ 345"int how" 346Copies 347.Fa len 348bytes data from buffer 349.Fa cp 350back into the mbuf chain 351.Fa m0 352as 353.Fn m_copyback 354does. 355Unlike 356.Fn m_copyback , 357it is safe to use 358.Fn m_copyback_cow 359on read-only mbufs. 360If needed, 361.Fn m_copyback_cow 362automatically allocates new mbufs and adjusts the chain. 363It returns a pointer to the resulting mbuf chain on success. 364Otherwise, it returns 365.Dv NULL . 366In that case, the original mbuf 367.Fa m0 368will be freed. 369The 370.Fa how 371parameter is a choice of 372.Dv M_WAIT / M_DONTWAIT 373from the caller. 374Unlike 375.Fn m_copyback , 376extending the mbuf chain isn't supported. 377It is an error to attempt to extend the mbuf chain using 378.Fn m_copyback_cow . 379.It Fn m_makewritable "struct mbuf **mp" "int off" "int len" "int how" 380Rearranges an mbuf chain so that 381.Fa len 382bytes from offset 383.Fa off 384are writable. 385When it meets read-only mbufs, it allocates new mbufs, adjusts the chain as 386.Fn m_copyback_cow 387does, and copies the original content into them. 388The 389.Fa how 390parameter is a choice of 391.Dv M_WAIT / M_DONTWAIT 392from the caller. 393.Fn m_makewritable 394preserves the contents of the mbuf chain even in the case of failure. 395It updates a pointer to the mbuf chain pointed to by 396.Fa mp . 397It returns 0 on success. 398Otherwise, it returns an error code, typically 399.Er ENOBUFS . 400.It Fn m_cat "struct mbuf *m" "struct mbuf *n" 401Concatenates mbuf chain 402.Fa n 403to 404.Fa m . 405Both chains must be of the same type; packet headers will 406.Em not 407be updated if present. 408.It Fn m_dup "struct mbuf *m" "int off0" "int len" "int wait" 409Similarly to 410.Fn m_copym , 411the function creates a copy of an mbuf chain starting 412.Fa off0 413bytes from the beginning, continuing for 414.Fa len 415bytes. 416While 417.Fn m_copym 418tries to share external storage for mbufs with 419.Dv M_EXT 420flag, 421.Fn m_dup 422will deep-copy the whole data content into new mbuf chain 423and avoids shared external storage. 424.It Fn m_prepend "struct mbuf *m" "int len" "int how" 425Lesser-used path for 426.Fn M_PREPEND : 427allocates new mbuf 428.Fa m 429of size 430.Fa len 431to prepend to the chain, copying junk along. 432The 433.Fa how 434parameter is a choice of 435.Dv M_WAIT / M_DONTWAIT 436from caller. 437.It Fn m_pulldown "struct mbuf *m" "int off" "int len" "int *offp" 438Rearranges an mbuf chain so that 439.Fa len 440bytes from offset 441.Fa off 442are contiguous and in the data area of an mbuf. 443The return value points to an mbuf in the middle of the mbuf chain 444.Fa m . 445If we call the return value 446.Fa n , 447the contiguous data region is available at 448.Li "mtod(n, caddr_t) + *offp" , 449or 450.Li "mtod(n, caddr_t)" 451if 452.Fa offp 453is 454.Dv NULL . 455The top of the mbuf chain 456.Fa m , 457and mbufs up to 458.Fa off , 459will not be modified. 460On successful return, it is guaranteed that the mbuf pointed to by 461.Fa n 462does not have a shared external storage, 463therefore it is safe to update the contiguous region. 464Returns 465.Dv NULL 466and frees the mbuf chain on failure. 467.Fa len 468must be smaller or equal than 469.Dv MCLBYTES . 470.It Fn m_pullup "struct mbuf *m" "int len" 471Rearranges an mbuf chain so that 472.Fa len 473bytes are contiguous 474and in the data area of an mbuf (so that 475.Fn mtod 476will work for a structure of size 477.Fa len ) . 478Returns the resulting 479mbuf chain on success, frees it and returns 480.Dv NULL 481on failure. 482If there is room, it will add up to 483.Dv max_protohdr 484- 485.Fa len 486extra bytes to the 487contiguous region to possibly avoid being called again. 488.Fa len 489must be smaller or equal than 490.Dv MHLEN . 491.It Fn m_split "struct mbuf *m0" "int len0" "int wait" 492Partitions an mbuf chain in two pieces, returning the tail, 493which is all but the first 494.Fa len0 495bytes. 496In case of failure, it returns 497.Dv NULL 498and attempts to 499restore the chain to its original state. 500.It Fn m_adj "struct mbuf *mp" "int req_len" 501Shaves off 502.Fa req_len 503bytes from head or tail of the (valid) data area. 504If 505.Fa req_len 506is greater than zero, front bytes are being shaved off, if it's smaller, 507from the back (and if it is zero, the mbuf will stay bearded). 508This function does not move data in any way, but is used to manipulate the 509data area pointer and data length variable of the mbuf in a non-clobbering 510way. 511.It Fn m_apply "struct mbuf *m" "int off" "int len" "int (*f)(void *, caddr_t, unsigned int)" "void *arg" 512Apply function 513.Fa f 514to the data in an mbuf chain starting 515.Fa off 516bytes from the beginning, continuing for 517.Fa len 518bytes. 519Neither 520.Fa off 521nor 522.Fa len 523may be negative. 524.Fa arg 525will be supplied as first argument for 526.Fa f , 527the second argument will be the pointer to the data buffer of a 528packet (starting after 529.Fa off 530bytes in the stream), and the third argument is the amount 531of data in bytes in this call. 532If 533.Fa f 534returns something not equal to zero 535.Fn m_apply 536will bail out, returning the return code of 537.Fa f . 538Upon successful completion it will return zero. 539.It Fn m_free "struct mbuf *m" 540Frees mbuf 541.Fa m . 542.It Fn m_freem "struct mbuf *m" 543Frees the mbuf chain beginning with 544.Fa m . 545This function contains the elementary sanity check for a 546.Dv NULL 547pointer. 548.It Fn mtod "struct mbuf *m" "datatype" 549Returns a pointer to the data contained in the specified mbuf 550.Fa m , 551type-casted to the specified data type 552.Fa datatype . 553Implemented as a macro. 554.It Fn MGET "struct mbuf *m" "int how" "int type" 555Allocates mbuf 556.Fa m 557and initializes it to contain internal data. 558See 559.Fn m_get . 560Implemented as a macro. 561.It Fn MGETHDR "struct mbuf *m" "int how" "int type" 562Allocates mbuf 563.Fa m 564and initializes it to contain a packet header. 565See 566.Fn m_gethdr . 567Implemented as a macro. 568.It Fn MEXTMALLOC "struct mbuf *m" "int len" "int how" 569Allocates external storage of size 570.Fa len 571for mbuf 572.Fa m . 573The 574.Fa how 575parameter is a choice of 576.Dv M_WAIT / M_DONTWAIT 577from caller. 578The flag 579.Dv M_EXT 580is set upon success. 581Implemented as a macro. 582.It Fn MEXTADD "struct mbuf *m" "caddr_t buf" "int size" "int type" "void (*free)(struct mbuf *, caddr_t, size_t, void *)" "void *arg" 583Adds pre-allocated external storage 584.Fa buf 585to a normal mbuf 586.Fa m ; 587the parameters 588.Fa size , 589.Fa type , 590.Fa free 591and 592.Fa arg 593describe the external storage. 594.Fa size 595is the size of the storage, 596.Fa type 597describes its 598.Xr malloc 9 599type, 600.Fa free 601is a free routine (if not the usual one), and 602.Fa arg 603is a possible argument to the free routine. 604The flag 605.Dv M_EXT 606is set upon success. 607Implemented as a macro. 608If a free routine is specified, it will be called when the mbuf is freed or 609when MEXTREMOVE is called for the mbuf. 610In the case of former, the first argument for a free routine is the mbuf 611.Fa m 612and the routine is expected to free it in addition to the external storage 613pointed by second argument. 614In the case of latter, the first argument for the routine is NULL. 615.It Fn MCLGET "struct mbuf *m" "int how" 616Allocates and adds an mbuf cluster to a normal mbuf 617.Fa m . 618The 619.Fa how 620parameter is a choice of 621.Dv M_WAIT / M_DONTWAIT 622from caller. 623The flag 624.Dv M_EXT 625is set upon success. 626Implemented as a macro. 627.It Fn M_COPY_PKTHDR "struct mbuf *to" "struct mbuf *from" 628Copies the mbuf pkthdr from mbuf 629.Fa from 630to mbuf 631.Fa to . 632.Fa from 633must have the type flag 634.Dv M_PKTHDR 635set, and 636.Fa to 637must be empty. 638Implemented as a macro. 639.It Fn M_MOVE_PKTHDR "struct mbuf *to" "struct mbuf *from" 640Moves the mbuf pkthdr from mbuf 641.Fa from 642to mbuf 643.Fa to . 644.Fa from 645must have the type flag 646.Dv M_PKTHDR 647set, and 648.Fa to 649must be empty. 650The flag 651.Dv M_PKTHDR 652in mbuf 653.Fa from 654will be cleared. 655.It Fn M_ALIGN "struct mbuf *m" "int len" 656Sets the data pointer of a newly allocated mbuf 657.Fa m 658to 659.Fa len 660bytes from the end of the mbuf data area, so that 661.Fa len 662bytes of data written to the mbuf 663.Fa m , 664starting at the data pointer, will be aligned to the end of the data area. 665Implemented as a macro. 666.It Fn MH_ALIGN "struct mbuf *m" "int len" 667Sets the data pointer of a newly allocated packetheader mbuf 668.Fa m 669to 670.Fa len 671bytes from the end of the mbuf data area, so that 672.Fa len 673bytes of data written to the mbuf 674.Fa m , 675starting at the data pointer, will be aligned to the end of the data area. 676Implemented as a macro. 677.It Fn M_LEADINGSPACE "struct mbuf *m" 678Returns the amount of space available before the current start of valid 679data in mbuf 680.Fa m . 681Returns 0 if the mbuf data part is shared across multiple mbufs 682.Pq i.e. not writable . 683Implemented as a macro. 684.It Fn M_TRAILINGSPACE "struct mbuf *m" 685Returns the amount of space available after the current end of valid 686data in mbuf 687.Fa m . 688Returns 0 if the mbuf data part is shared across multiple mbufs 689.Pq i.e. not writable . 690Implemented as a macro. 691.It Fn M_PREPEND "struct mbuf *m" "int plen" "int how" 692Prepends space of size 693.Fa plen 694to mbuf 695.Fa m . 696If a new mbuf must be allocated, 697.Fa how 698specifies whether to wait. 699If 700.Fa how 701is 702.Dv M_DONTWAIT 703and allocation fails, the original mbuf chain is freed and 704.Fa m 705is set to 706.Dv NULL . 707Implemented as a macro. 708.It Fn MCHTYPE "struct mbuf *m" "int type" 709Change mbuf 710.Fa m 711to new type 712.Fa type . 713Implemented as a macro. 714.It Fn MEXTREMOVE "struct mbuf *m" 715Removes external storage from mbuf 716.Fa m . 717The flag 718.Dv M_EXT 719is removed. 720Implemented as a macro. 721.It Fn MFREE "struct mbuf *m" "struct mbuf *n" 722Frees a single mbuf 723.Fa m 724and places the successor, if any, in mbuf 725.Fa n . 726Implemented as a macro. 727.El 728.Sh FILES 729The 730.Nm 731management functions are implemented within the file 732.Pa sys/kern/uipc_mbuf.c . 733Function prototypes, and the functions implemented as macros 734are located in 735.Pa sys/sys/mbuf.h . 736Both pathnames are relative to the root of the 737.Nx 738source tree, 739.Pa /usr/src . 740.Sh SEE ALSO 741.Pa /usr/share/doc/smm/18.net , 742.Xr netstat 1 , 743.Xr m_tag 9 , 744.Xr malloc 9 745.Rs 746.%A Jun-ichiro Hagino 747.%T "Mbuf issues in 4.4BSD IPv6/IPsec support (experiences from KAME IPv6/IPsec implementation)" 748.%B "Proceedings of the freenix track: 2000 USENIX annual technical conference" 749.%D June 2000 750.Re 751.Sh AUTHORS 752.An -nosplit 753The original mbuf data structures were designed by Rob Gurwitz 754when he did the initial TCP/IP implementation at BBN. 755.br 756Further extensions and enhancements were made by Bill Joy, Sam Leffler, 757and Mike Karels at CSRG. 758.br 759Current implementation of external storage by 760.An Matt Thomas 761.Aq matt@3am-software.com 762and 763.An Jason R. Thorpe 764.Aq thorpej@NetBSD.org . 765