xref: /original-bsd/sys/kern/uipc_socket2.c (revision dc6e2994)
1 /*
2  * Copyright (c) 1982, 1986, 1988, 1990, 1993
3  *	The Regents of the University of California.  All rights reserved.
4  *
5  * %sccs.include.redist.c%
6  *
7  *	@(#)uipc_socket2.c	8.2 (Berkeley) 02/14/95
8  */
9 
10 #include <sys/param.h>
11 #include <sys/systm.h>
12 #include <sys/proc.h>
13 #include <sys/file.h>
14 #include <sys/buf.h>
15 #include <sys/malloc.h>
16 #include <sys/mbuf.h>
17 #include <sys/protosw.h>
18 #include <sys/socket.h>
19 #include <sys/socketvar.h>
20 
21 /*
22  * Primitive routines for operating on sockets and socket buffers
23  */
24 
25 /* strings for sleep message: */
26 char	netio[] = "netio";
27 char	netcon[] = "netcon";
28 char	netcls[] = "netcls";
29 
30 u_long	sb_max = SB_MAX;		/* patchable */
31 
32 /*
33  * Procedures to manipulate state flags of socket
34  * and do appropriate wakeups.  Normal sequence from the
35  * active (originating) side is that soisconnecting() is
36  * called during processing of connect() call,
37  * resulting in an eventual call to soisconnected() if/when the
38  * connection is established.  When the connection is torn down
39  * soisdisconnecting() is called during processing of disconnect() call,
40  * and soisdisconnected() is called when the connection to the peer
41  * is totally severed.  The semantics of these routines are such that
42  * connectionless protocols can call soisconnected() and soisdisconnected()
43  * only, bypassing the in-progress calls when setting up a ``connection''
44  * takes no time.
45  *
46  * From the passive side, a socket is created with
47  * two queues of sockets: so_q0 for connections in progress
48  * and so_q for connections already made and awaiting user acceptance.
49  * As a protocol is preparing incoming connections, it creates a socket
50  * structure queued on so_q0 by calling sonewconn().  When the connection
51  * is established, soisconnected() is called, and transfers the
52  * socket structure to so_q, making it available to accept().
53  *
54  * If a socket is closed with sockets on either
55  * so_q0 or so_q, these sockets are dropped.
56  *
57  * If higher level protocols are implemented in
58  * the kernel, the wakeups done here will sometimes
59  * cause software-interrupt process scheduling.
60  */
61 
62 void
soisconnecting(so)63 soisconnecting(so)
64 	register struct socket *so;
65 {
66 
67 	so->so_state &= ~(SS_ISCONNECTED|SS_ISDISCONNECTING);
68 	so->so_state |= SS_ISCONNECTING;
69 }
70 
71 void
soisconnected(so)72 soisconnected(so)
73 	register struct socket *so;
74 {
75 	register struct socket *head = so->so_head;
76 
77 	so->so_state &= ~(SS_ISCONNECTING|SS_ISDISCONNECTING|SS_ISCONFIRMING);
78 	so->so_state |= SS_ISCONNECTED;
79 	if (head && soqremque(so, 0)) {
80 		soqinsque(head, so, 1);
81 		sorwakeup(head);
82 		wakeup((caddr_t)&head->so_timeo);
83 	} else {
84 		wakeup((caddr_t)&so->so_timeo);
85 		sorwakeup(so);
86 		sowwakeup(so);
87 	}
88 }
89 
90 void
soisdisconnecting(so)91 soisdisconnecting(so)
92 	register struct socket *so;
93 {
94 
95 	so->so_state &= ~SS_ISCONNECTING;
96 	so->so_state |= (SS_ISDISCONNECTING|SS_CANTRCVMORE|SS_CANTSENDMORE);
97 	wakeup((caddr_t)&so->so_timeo);
98 	sowwakeup(so);
99 	sorwakeup(so);
100 }
101 
102 void
soisdisconnected(so)103 soisdisconnected(so)
104 	register struct socket *so;
105 {
106 
107 	so->so_state &= ~(SS_ISCONNECTING|SS_ISCONNECTED|SS_ISDISCONNECTING);
108 	so->so_state |= (SS_CANTRCVMORE|SS_CANTSENDMORE);
109 	wakeup((caddr_t)&so->so_timeo);
110 	sowwakeup(so);
111 	sorwakeup(so);
112 }
113 
114 /*
115  * When an attempt at a new connection is noted on a socket
116  * which accepts connections, sonewconn is called.  If the
117  * connection is possible (subject to space constraints, etc.)
118  * then we allocate a new structure, propoerly linked into the
119  * data structure of the original socket, and return this.
120  * Connstatus may be 0, or SO_ISCONFIRMING, or SO_ISCONNECTED.
121  *
122  * Currently, sonewconn() is defined as sonewconn1() in socketvar.h
123  * to catch calls that are missing the (new) second parameter.
124  */
125 struct socket *
sonewconn1(head,connstatus)126 sonewconn1(head, connstatus)
127 	register struct socket *head;
128 	int connstatus;
129 {
130 	register struct socket *so;
131 	int soqueue = connstatus ? 1 : 0;
132 
133 	if (head->so_qlen + head->so_q0len > 3 * head->so_qlimit / 2)
134 		return ((struct socket *)0);
135 	MALLOC(so, struct socket *, sizeof(*so), M_SOCKET, M_DONTWAIT);
136 	if (so == NULL)
137 		return ((struct socket *)0);
138 	bzero((caddr_t)so, sizeof(*so));
139 	so->so_type = head->so_type;
140 	so->so_options = head->so_options &~ SO_ACCEPTCONN;
141 	so->so_linger = head->so_linger;
142 	so->so_state = head->so_state | SS_NOFDREF;
143 	so->so_proto = head->so_proto;
144 	so->so_timeo = head->so_timeo;
145 	so->so_pgid = head->so_pgid;
146 	(void) soreserve(so, head->so_snd.sb_hiwat, head->so_rcv.sb_hiwat);
147 	soqinsque(head, so, soqueue);
148 	if ((*so->so_proto->pr_usrreq)(so, PRU_ATTACH,
149 	    (struct mbuf *)0, (struct mbuf *)0, (struct mbuf *)0)) {
150 		(void) soqremque(so, soqueue);
151 		(void) free((caddr_t)so, M_SOCKET);
152 		return ((struct socket *)0);
153 	}
154 	if (connstatus) {
155 		sorwakeup(head);
156 		wakeup((caddr_t)&head->so_timeo);
157 		so->so_state |= connstatus;
158 	}
159 	return (so);
160 }
161 
162 void
soqinsque(head,so,q)163 soqinsque(head, so, q)
164 	register struct socket *head, *so;
165 	int q;
166 {
167 
168 	register struct socket **prev;
169 	so->so_head = head;
170 	if (q == 0) {
171 		head->so_q0len++;
172 		so->so_q0 = 0;
173 		for (prev = &(head->so_q0); *prev; )
174 			prev = &((*prev)->so_q0);
175 	} else {
176 		head->so_qlen++;
177 		so->so_q = 0;
178 		for (prev = &(head->so_q); *prev; )
179 			prev = &((*prev)->so_q);
180 	}
181 	*prev = so;
182 }
183 
184 int
soqremque(so,q)185 soqremque(so, q)
186 	register struct socket *so;
187 	int q;
188 {
189 	register struct socket *head, *prev, *next;
190 
191 	head = so->so_head;
192 	prev = head;
193 	for (;;) {
194 		next = q ? prev->so_q : prev->so_q0;
195 		if (next == so)
196 			break;
197 		if (next == 0)
198 			return (0);
199 		prev = next;
200 	}
201 	if (q == 0) {
202 		prev->so_q0 = next->so_q0;
203 		head->so_q0len--;
204 	} else {
205 		prev->so_q = next->so_q;
206 		head->so_qlen--;
207 	}
208 	next->so_q0 = next->so_q = 0;
209 	next->so_head = 0;
210 	return (1);
211 }
212 
213 /*
214  * Socantsendmore indicates that no more data will be sent on the
215  * socket; it would normally be applied to a socket when the user
216  * informs the system that no more data is to be sent, by the protocol
217  * code (in case PRU_SHUTDOWN).  Socantrcvmore indicates that no more data
218  * will be received, and will normally be applied to the socket by a
219  * protocol when it detects that the peer will send no more data.
220  * Data queued for reading in the socket may yet be read.
221  */
222 
223 void
socantsendmore(so)224 socantsendmore(so)
225 	struct socket *so;
226 {
227 
228 	so->so_state |= SS_CANTSENDMORE;
229 	sowwakeup(so);
230 }
231 
232 void
socantrcvmore(so)233 socantrcvmore(so)
234 	struct socket *so;
235 {
236 
237 	so->so_state |= SS_CANTRCVMORE;
238 	sorwakeup(so);
239 }
240 
241 /*
242  * Wait for data to arrive at/drain from a socket buffer.
243  */
244 int
sbwait(sb)245 sbwait(sb)
246 	struct sockbuf *sb;
247 {
248 
249 	sb->sb_flags |= SB_WAIT;
250 	return (tsleep((caddr_t)&sb->sb_cc,
251 	    (sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK | PCATCH, netio,
252 	    sb->sb_timeo));
253 }
254 
255 /*
256  * Lock a sockbuf already known to be locked;
257  * return any error returned from sleep (EINTR).
258  */
259 int
sb_lock(sb)260 sb_lock(sb)
261 	register struct sockbuf *sb;
262 {
263 	int error;
264 
265 	while (sb->sb_flags & SB_LOCK) {
266 		sb->sb_flags |= SB_WANT;
267 		if (error = tsleep((caddr_t)&sb->sb_flags,
268 		    (sb->sb_flags & SB_NOINTR) ? PSOCK : PSOCK|PCATCH,
269 		    netio, 0))
270 			return (error);
271 	}
272 	sb->sb_flags |= SB_LOCK;
273 	return (0);
274 }
275 
276 /*
277  * Wakeup processes waiting on a socket buffer.
278  * Do asynchronous notification via SIGIO
279  * if the socket has the SS_ASYNC flag set.
280  */
281 void
sowakeup(so,sb)282 sowakeup(so, sb)
283 	register struct socket *so;
284 	register struct sockbuf *sb;
285 {
286 	struct proc *p;
287 
288 	selwakeup(&sb->sb_sel);
289 	sb->sb_flags &= ~SB_SEL;
290 	if (sb->sb_flags & SB_WAIT) {
291 		sb->sb_flags &= ~SB_WAIT;
292 		wakeup((caddr_t)&sb->sb_cc);
293 	}
294 	if (so->so_state & SS_ASYNC) {
295 		if (so->so_pgid < 0)
296 			gsignal(-so->so_pgid, SIGIO);
297 		else if (so->so_pgid > 0 && (p = pfind(so->so_pgid)) != 0)
298 			psignal(p, SIGIO);
299 	}
300 }
301 
302 /*
303  * Socket buffer (struct sockbuf) utility routines.
304  *
305  * Each socket contains two socket buffers: one for sending data and
306  * one for receiving data.  Each buffer contains a queue of mbufs,
307  * information about the number of mbufs and amount of data in the
308  * queue, and other fields allowing select() statements and notification
309  * on data availability to be implemented.
310  *
311  * Data stored in a socket buffer is maintained as a list of records.
312  * Each record is a list of mbufs chained together with the m_next
313  * field.  Records are chained together with the m_nextpkt field. The upper
314  * level routine soreceive() expects the following conventions to be
315  * observed when placing information in the receive buffer:
316  *
317  * 1. If the protocol requires each message be preceded by the sender's
318  *    name, then a record containing that name must be present before
319  *    any associated data (mbuf's must be of type MT_SONAME).
320  * 2. If the protocol supports the exchange of ``access rights'' (really
321  *    just additional data associated with the message), and there are
322  *    ``rights'' to be received, then a record containing this data
323  *    should be present (mbuf's must be of type MT_RIGHTS).
324  * 3. If a name or rights record exists, then it must be followed by
325  *    a data record, perhaps of zero length.
326  *
327  * Before using a new socket structure it is first necessary to reserve
328  * buffer space to the socket, by calling sbreserve().  This should commit
329  * some of the available buffer space in the system buffer pool for the
330  * socket (currently, it does nothing but enforce limits).  The space
331  * should be released by calling sbrelease() when the socket is destroyed.
332  */
333 
334 int
soreserve(so,sndcc,rcvcc)335 soreserve(so, sndcc, rcvcc)
336 	register struct socket *so;
337 	u_long sndcc, rcvcc;
338 {
339 
340 	if (sbreserve(&so->so_snd, sndcc) == 0)
341 		goto bad;
342 	if (sbreserve(&so->so_rcv, rcvcc) == 0)
343 		goto bad2;
344 	if (so->so_rcv.sb_lowat == 0)
345 		so->so_rcv.sb_lowat = 1;
346 	if (so->so_snd.sb_lowat == 0)
347 		so->so_snd.sb_lowat = MCLBYTES;
348 	if (so->so_snd.sb_lowat > so->so_snd.sb_hiwat)
349 		so->so_snd.sb_lowat = so->so_snd.sb_hiwat;
350 	return (0);
351 bad2:
352 	sbrelease(&so->so_snd);
353 bad:
354 	return (ENOBUFS);
355 }
356 
357 /*
358  * Allot mbufs to a sockbuf.
359  * Attempt to scale mbmax so that mbcnt doesn't become limiting
360  * if buffering efficiency is near the normal case.
361  */
362 int
sbreserve(sb,cc)363 sbreserve(sb, cc)
364 	struct sockbuf *sb;
365 	u_long cc;
366 {
367 
368 	if (cc > sb_max * MCLBYTES / (MSIZE + MCLBYTES))
369 		return (0);
370 	sb->sb_hiwat = cc;
371 	sb->sb_mbmax = min(cc * 2, sb_max);
372 	if (sb->sb_lowat > sb->sb_hiwat)
373 		sb->sb_lowat = sb->sb_hiwat;
374 	return (1);
375 }
376 
377 /*
378  * Free mbufs held by a socket, and reserved mbuf space.
379  */
380 void
sbrelease(sb)381 sbrelease(sb)
382 	struct sockbuf *sb;
383 {
384 
385 	sbflush(sb);
386 	sb->sb_hiwat = sb->sb_mbmax = 0;
387 }
388 
389 /*
390  * Routines to add and remove
391  * data from an mbuf queue.
392  *
393  * The routines sbappend() or sbappendrecord() are normally called to
394  * append new mbufs to a socket buffer, after checking that adequate
395  * space is available, comparing the function sbspace() with the amount
396  * of data to be added.  sbappendrecord() differs from sbappend() in
397  * that data supplied is treated as the beginning of a new record.
398  * To place a sender's address, optional access rights, and data in a
399  * socket receive buffer, sbappendaddr() should be used.  To place
400  * access rights and data in a socket receive buffer, sbappendrights()
401  * should be used.  In either case, the new data begins a new record.
402  * Note that unlike sbappend() and sbappendrecord(), these routines check
403  * for the caller that there will be enough space to store the data.
404  * Each fails if there is not enough space, or if it cannot find mbufs
405  * to store additional information in.
406  *
407  * Reliable protocols may use the socket send buffer to hold data
408  * awaiting acknowledgement.  Data is normally copied from a socket
409  * send buffer in a protocol with m_copy for output to a peer,
410  * and then removing the data from the socket buffer with sbdrop()
411  * or sbdroprecord() when the data is acknowledged by the peer.
412  */
413 
414 /*
415  * Append mbuf chain m to the last record in the
416  * socket buffer sb.  The additional space associated
417  * the mbuf chain is recorded in sb.  Empty mbufs are
418  * discarded and mbufs are compacted where possible.
419  */
420 void
sbappend(sb,m)421 sbappend(sb, m)
422 	struct sockbuf *sb;
423 	struct mbuf *m;
424 {
425 	register struct mbuf *n;
426 
427 	if (m == 0)
428 		return;
429 	if (n = sb->sb_mb) {
430 		while (n->m_nextpkt)
431 			n = n->m_nextpkt;
432 		do {
433 			if (n->m_flags & M_EOR) {
434 				sbappendrecord(sb, m); /* XXXXXX!!!! */
435 				return;
436 			}
437 		} while (n->m_next && (n = n->m_next));
438 	}
439 	sbcompress(sb, m, n);
440 }
441 
442 #ifdef SOCKBUF_DEBUG
443 void
sbcheck(sb)444 sbcheck(sb)
445 	register struct sockbuf *sb;
446 {
447 	register struct mbuf *m;
448 	register int len = 0, mbcnt = 0;
449 
450 	for (m = sb->sb_mb; m; m = m->m_next) {
451 		len += m->m_len;
452 		mbcnt += MSIZE;
453 		if (m->m_flags & M_EXT)
454 			mbcnt += m->m_ext.ext_size;
455 		if (m->m_nextpkt)
456 			panic("sbcheck nextpkt");
457 	}
458 	if (len != sb->sb_cc || mbcnt != sb->sb_mbcnt) {
459 		printf("cc %d != %d || mbcnt %d != %d\n", len, sb->sb_cc,
460 		    mbcnt, sb->sb_mbcnt);
461 		panic("sbcheck");
462 	}
463 }
464 #endif
465 
466 /*
467  * As above, except the mbuf chain
468  * begins a new record.
469  */
470 void
sbappendrecord(sb,m0)471 sbappendrecord(sb, m0)
472 	register struct sockbuf *sb;
473 	register struct mbuf *m0;
474 {
475 	register struct mbuf *m;
476 
477 	if (m0 == 0)
478 		return;
479 	if (m = sb->sb_mb)
480 		while (m->m_nextpkt)
481 			m = m->m_nextpkt;
482 	/*
483 	 * Put the first mbuf on the queue.
484 	 * Note this permits zero length records.
485 	 */
486 	sballoc(sb, m0);
487 	if (m)
488 		m->m_nextpkt = m0;
489 	else
490 		sb->sb_mb = m0;
491 	m = m0->m_next;
492 	m0->m_next = 0;
493 	if (m && (m0->m_flags & M_EOR)) {
494 		m0->m_flags &= ~M_EOR;
495 		m->m_flags |= M_EOR;
496 	}
497 	sbcompress(sb, m, m0);
498 }
499 
500 /*
501  * As above except that OOB data
502  * is inserted at the beginning of the sockbuf,
503  * but after any other OOB data.
504  */
505 void
sbinsertoob(sb,m0)506 sbinsertoob(sb, m0)
507 	register struct sockbuf *sb;
508 	register struct mbuf *m0;
509 {
510 	register struct mbuf *m;
511 	register struct mbuf **mp;
512 
513 	if (m0 == 0)
514 		return;
515 	for (mp = &sb->sb_mb; m = *mp; mp = &((*mp)->m_nextpkt)) {
516 	    again:
517 		switch (m->m_type) {
518 
519 		case MT_OOBDATA:
520 			continue;		/* WANT next train */
521 
522 		case MT_CONTROL:
523 			if (m = m->m_next)
524 				goto again;	/* inspect THIS train further */
525 		}
526 		break;
527 	}
528 	/*
529 	 * Put the first mbuf on the queue.
530 	 * Note this permits zero length records.
531 	 */
532 	sballoc(sb, m0);
533 	m0->m_nextpkt = *mp;
534 	*mp = m0;
535 	m = m0->m_next;
536 	m0->m_next = 0;
537 	if (m && (m0->m_flags & M_EOR)) {
538 		m0->m_flags &= ~M_EOR;
539 		m->m_flags |= M_EOR;
540 	}
541 	sbcompress(sb, m, m0);
542 }
543 
544 /*
545  * Append address and data, and optionally, control (ancillary) data
546  * to the receive queue of a socket.  If present,
547  * m0 must include a packet header with total length.
548  * Returns 0 if no space in sockbuf or insufficient mbufs.
549  */
550 int
sbappendaddr(sb,asa,m0,control)551 sbappendaddr(sb, asa, m0, control)
552 	register struct sockbuf *sb;
553 	struct sockaddr *asa;
554 	struct mbuf *m0, *control;
555 {
556 	register struct mbuf *m, *n;
557 	int space = asa->sa_len;
558 
559 if (m0 && (m0->m_flags & M_PKTHDR) == 0)
560 panic("sbappendaddr");
561 	if (m0)
562 		space += m0->m_pkthdr.len;
563 	for (n = control; n; n = n->m_next) {
564 		space += n->m_len;
565 		if (n->m_next == 0)	/* keep pointer to last control buf */
566 			break;
567 	}
568 	if (space > sbspace(sb))
569 		return (0);
570 	if (asa->sa_len > MLEN)
571 		return (0);
572 	MGET(m, M_DONTWAIT, MT_SONAME);
573 	if (m == 0)
574 		return (0);
575 	m->m_len = asa->sa_len;
576 	bcopy((caddr_t)asa, mtod(m, caddr_t), asa->sa_len);
577 	if (n)
578 		n->m_next = m0;		/* concatenate data to control */
579 	else
580 		control = m0;
581 	m->m_next = control;
582 	for (n = m; n; n = n->m_next)
583 		sballoc(sb, n);
584 	if (n = sb->sb_mb) {
585 		while (n->m_nextpkt)
586 			n = n->m_nextpkt;
587 		n->m_nextpkt = m;
588 	} else
589 		sb->sb_mb = m;
590 	return (1);
591 }
592 
593 int
sbappendcontrol(sb,m0,control)594 sbappendcontrol(sb, m0, control)
595 	struct sockbuf *sb;
596 	struct mbuf *m0, *control;
597 {
598 	register struct mbuf *m, *n;
599 	int space = 0;
600 
601 	if (control == 0)
602 		panic("sbappendcontrol");
603 	for (m = control; ; m = m->m_next) {
604 		space += m->m_len;
605 		if (m->m_next == 0)
606 			break;
607 	}
608 	n = m;			/* save pointer to last control buffer */
609 	for (m = m0; m; m = m->m_next)
610 		space += m->m_len;
611 	if (space > sbspace(sb))
612 		return (0);
613 	n->m_next = m0;			/* concatenate data to control */
614 	for (m = control; m; m = m->m_next)
615 		sballoc(sb, m);
616 	if (n = sb->sb_mb) {
617 		while (n->m_nextpkt)
618 			n = n->m_nextpkt;
619 		n->m_nextpkt = control;
620 	} else
621 		sb->sb_mb = control;
622 	return (1);
623 }
624 
625 /*
626  * Compress mbuf chain m into the socket
627  * buffer sb following mbuf n.  If n
628  * is null, the buffer is presumed empty.
629  */
630 void
sbcompress(sb,m,n)631 sbcompress(sb, m, n)
632 	register struct sockbuf *sb;
633 	register struct mbuf *m, *n;
634 {
635 	register int eor = 0;
636 	register struct mbuf *o;
637 
638 	while (m) {
639 		eor |= m->m_flags & M_EOR;
640 		if (m->m_len == 0 &&
641 		    (eor == 0 ||
642 		     (((o = m->m_next) || (o = n)) &&
643 		      o->m_type == m->m_type))) {
644 			m = m_free(m);
645 			continue;
646 		}
647 		if (n && (n->m_flags & (M_EXT | M_EOR)) == 0 &&
648 		    (n->m_data + n->m_len + m->m_len) < &n->m_dat[MLEN] &&
649 		    n->m_type == m->m_type) {
650 			bcopy(mtod(m, caddr_t), mtod(n, caddr_t) + n->m_len,
651 			    (unsigned)m->m_len);
652 			n->m_len += m->m_len;
653 			sb->sb_cc += m->m_len;
654 			m = m_free(m);
655 			continue;
656 		}
657 		if (n)
658 			n->m_next = m;
659 		else
660 			sb->sb_mb = m;
661 		sballoc(sb, m);
662 		n = m;
663 		m->m_flags &= ~M_EOR;
664 		m = m->m_next;
665 		n->m_next = 0;
666 	}
667 	if (eor) {
668 		if (n)
669 			n->m_flags |= eor;
670 		else
671 			printf("semi-panic: sbcompress\n");
672 	}
673 }
674 
675 /*
676  * Free all mbufs in a sockbuf.
677  * Check that all resources are reclaimed.
678  */
679 void
sbflush(sb)680 sbflush(sb)
681 	register struct sockbuf *sb;
682 {
683 
684 	if (sb->sb_flags & SB_LOCK)
685 		panic("sbflush");
686 	while (sb->sb_mbcnt)
687 		sbdrop(sb, (int)sb->sb_cc);
688 	if (sb->sb_cc || sb->sb_mb)
689 		panic("sbflush 2");
690 }
691 
692 /*
693  * Drop data from (the front of) a sockbuf.
694  */
695 void
sbdrop(sb,len)696 sbdrop(sb, len)
697 	register struct sockbuf *sb;
698 	register int len;
699 {
700 	register struct mbuf *m, *mn;
701 	struct mbuf *next;
702 
703 	next = (m = sb->sb_mb) ? m->m_nextpkt : 0;
704 	while (len > 0) {
705 		if (m == 0) {
706 			if (next == 0)
707 				panic("sbdrop");
708 			m = next;
709 			next = m->m_nextpkt;
710 			continue;
711 		}
712 		if (m->m_len > len) {
713 			m->m_len -= len;
714 			m->m_data += len;
715 			sb->sb_cc -= len;
716 			break;
717 		}
718 		len -= m->m_len;
719 		sbfree(sb, m);
720 		MFREE(m, mn);
721 		m = mn;
722 	}
723 	while (m && m->m_len == 0) {
724 		sbfree(sb, m);
725 		MFREE(m, mn);
726 		m = mn;
727 	}
728 	if (m) {
729 		sb->sb_mb = m;
730 		m->m_nextpkt = next;
731 	} else
732 		sb->sb_mb = next;
733 }
734 
735 /*
736  * Drop a record off the front of a sockbuf
737  * and move the next record to the front.
738  */
739 void
sbdroprecord(sb)740 sbdroprecord(sb)
741 	register struct sockbuf *sb;
742 {
743 	register struct mbuf *m, *mn;
744 
745 	m = sb->sb_mb;
746 	if (m) {
747 		sb->sb_mb = m->m_nextpkt;
748 		do {
749 			sbfree(sb, m);
750 			MFREE(m, mn);
751 		} while (m = mn);
752 	}
753 }
754