// SPDX-License-Identifier: GPL-2.0-or-later /* * PPP async serial channel driver for Linux. * * Copyright 1999 Paul Mackerras. * * This driver provides the encapsulation and framing for sending * and receiving PPP frames over async serial lines. It relies on * the generic PPP layer to give it frames to send and to process * received frames. It implements the PPP line discipline. * * Part of the code in this driver was inspired by the old async-only * PPP driver, written by Michael Callahan and Al Longyear, and * subsequently hacked by Paul Mackerras. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define PPP_VERSION "2.4.2" #define OBUFSIZE 4096 /* Structure for storing local state. */ struct asyncppp { struct tty_struct *tty; unsigned int flags; unsigned int state; unsigned int rbits; int mru; spinlock_t xmit_lock; spinlock_t recv_lock; unsigned long xmit_flags; u32 xaccm[8]; u32 raccm; unsigned int bytes_sent; unsigned int bytes_rcvd; struct sk_buff *tpkt; int tpkt_pos; u16 tfcs; unsigned char *optr; unsigned char *olim; unsigned long last_xmit; struct sk_buff *rpkt; int lcp_fcs; struct sk_buff_head rqueue; struct tasklet_struct tsk; refcount_t refcnt; struct completion dead; struct ppp_channel chan; /* interface to generic ppp layer */ unsigned char obuf[OBUFSIZE]; }; /* Bit numbers in xmit_flags */ #define XMIT_WAKEUP 0 #define XMIT_FULL 1 #define XMIT_BUSY 2 /* State bits */ #define SC_TOSS 1 #define SC_ESCAPE 2 #define SC_PREV_ERROR 4 /* Bits in rbits */ #define SC_RCV_BITS (SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP) static int flag_time = HZ; module_param(flag_time, int, 0); MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)"); MODULE_DESCRIPTION("PPP async serial channel module"); MODULE_LICENSE("GPL"); MODULE_ALIAS_LDISC(N_PPP); /* * Prototypes. */ static int ppp_async_encode(struct asyncppp *ap); static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb); static int ppp_async_push(struct asyncppp *ap); static void ppp_async_flush_output(struct asyncppp *ap); static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf, const u8 *flags, int count); static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg); static void ppp_async_process(struct tasklet_struct *t); static void async_lcp_peek(struct asyncppp *ap, unsigned char *data, int len, int inbound); static const struct ppp_channel_ops async_ops = { .start_xmit = ppp_async_send, .ioctl = ppp_async_ioctl, }; /* * Routines implementing the PPP line discipline. */ /* * We have a potential race on dereferencing tty->disc_data, * because the tty layer provides no locking at all - thus one * cpu could be running ppp_asynctty_receive while another * calls ppp_asynctty_close, which zeroes tty->disc_data and * frees the memory that ppp_asynctty_receive is using. The best * way to fix this is to use a rwlock in the tty struct, but for now * we use a single global rwlock for all ttys in ppp line discipline. * * FIXME: this is no longer true. The _close path for the ldisc is * now guaranteed to be sane. */ static DEFINE_RWLOCK(disc_data_lock); static struct asyncppp *ap_get(struct tty_struct *tty) { struct asyncppp *ap; read_lock(&disc_data_lock); ap = tty->disc_data; if (ap != NULL) refcount_inc(&ap->refcnt); read_unlock(&disc_data_lock); return ap; } static void ap_put(struct asyncppp *ap) { if (refcount_dec_and_test(&ap->refcnt)) complete(&ap->dead); } /* * Called when a tty is put into PPP line discipline. Called in process * context. */ static int ppp_asynctty_open(struct tty_struct *tty) { struct asyncppp *ap; int err; int speed; if (tty->ops->write == NULL) return -EOPNOTSUPP; err = -ENOMEM; ap = kzalloc(sizeof(*ap), GFP_KERNEL); if (!ap) goto out; /* initialize the asyncppp structure */ ap->tty = tty; ap->mru = PPP_MRU; spin_lock_init(&ap->xmit_lock); spin_lock_init(&ap->recv_lock); ap->xaccm[0] = ~0U; ap->xaccm[3] = 0x60000000U; ap->raccm = ~0U; ap->optr = ap->obuf; ap->olim = ap->obuf; ap->lcp_fcs = -1; skb_queue_head_init(&ap->rqueue); tasklet_setup(&ap->tsk, ppp_async_process); refcount_set(&ap->refcnt, 1); init_completion(&ap->dead); ap->chan.private = ap; ap->chan.ops = &async_ops; ap->chan.mtu = PPP_MRU; speed = tty_get_baud_rate(tty); ap->chan.speed = speed; err = ppp_register_channel(&ap->chan); if (err) goto out_free; tty->disc_data = ap; tty->receive_room = 65536; return 0; out_free: kfree(ap); out: return err; } /* * Called when the tty is put into another line discipline * or it hangs up. We have to wait for any cpu currently * executing in any of the other ppp_asynctty_* routines to * finish before we can call ppp_unregister_channel and free * the asyncppp struct. This routine must be called from * process context, not interrupt or softirq context. */ static void ppp_asynctty_close(struct tty_struct *tty) { struct asyncppp *ap; write_lock_irq(&disc_data_lock); ap = tty->disc_data; tty->disc_data = NULL; write_unlock_irq(&disc_data_lock); if (!ap) return; /* * We have now ensured that nobody can start using ap from now * on, but we have to wait for all existing users to finish. * Note that ppp_unregister_channel ensures that no calls to * our channel ops (i.e. ppp_async_send/ioctl) are in progress * by the time it returns. */ if (!refcount_dec_and_test(&ap->refcnt)) wait_for_completion(&ap->dead); tasklet_kill(&ap->tsk); ppp_unregister_channel(&ap->chan); kfree_skb(ap->rpkt); skb_queue_purge(&ap->rqueue); kfree_skb(ap->tpkt); kfree(ap); } /* * Called on tty hangup in process context. * * Wait for I/O to driver to complete and unregister PPP channel. * This is already done by the close routine, so just call that. */ static void ppp_asynctty_hangup(struct tty_struct *tty) { ppp_asynctty_close(tty); } /* * Read does nothing - no data is ever available this way. * Pppd reads and writes packets via /dev/ppp instead. */ static ssize_t ppp_asynctty_read(struct tty_struct *tty, struct file *file, u8 *buf, size_t count, void **cookie, unsigned long offset) { return -EAGAIN; } /* * Write on the tty does nothing, the packets all come in * from the ppp generic stuff. */ static ssize_t ppp_asynctty_write(struct tty_struct *tty, struct file *file, const u8 *buf, size_t count) { return -EAGAIN; } /* * Called in process context only. May be re-entered by multiple * ioctl calling threads. */ static int ppp_asynctty_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg) { struct asyncppp *ap = ap_get(tty); int err, val; int __user *p = (int __user *)arg; if (!ap) return -ENXIO; err = -EFAULT; switch (cmd) { case PPPIOCGCHAN: err = -EFAULT; if (put_user(ppp_channel_index(&ap->chan), p)) break; err = 0; break; case PPPIOCGUNIT: err = -EFAULT; if (put_user(ppp_unit_number(&ap->chan), p)) break; err = 0; break; case TCFLSH: /* flush our buffers and the serial port's buffer */ if (arg == TCIOFLUSH || arg == TCOFLUSH) ppp_async_flush_output(ap); err = n_tty_ioctl_helper(tty, cmd, arg); break; case FIONREAD: val = 0; if (put_user(val, p)) break; err = 0; break; default: /* Try the various mode ioctls */ err = tty_mode_ioctl(tty, cmd, arg); } ap_put(ap); return err; } /* May sleep, don't call from interrupt level or with interrupts disabled */ static void ppp_asynctty_receive(struct tty_struct *tty, const u8 *buf, const u8 *cflags, size_t count) { struct asyncppp *ap = ap_get(tty); unsigned long flags; if (!ap) return; spin_lock_irqsave(&ap->recv_lock, flags); ppp_async_input(ap, buf, cflags, count); spin_unlock_irqrestore(&ap->recv_lock, flags); if (!skb_queue_empty(&ap->rqueue)) tasklet_schedule(&ap->tsk); ap_put(ap); tty_unthrottle(tty); } static void ppp_asynctty_wakeup(struct tty_struct *tty) { struct asyncppp *ap = ap_get(tty); clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); if (!ap) return; set_bit(XMIT_WAKEUP, &ap->xmit_flags); tasklet_schedule(&ap->tsk); ap_put(ap); } static struct tty_ldisc_ops ppp_ldisc = { .owner = THIS_MODULE, .num = N_PPP, .name = "ppp", .open = ppp_asynctty_open, .close = ppp_asynctty_close, .hangup = ppp_asynctty_hangup, .read = ppp_asynctty_read, .write = ppp_asynctty_write, .ioctl = ppp_asynctty_ioctl, .receive_buf = ppp_asynctty_receive, .write_wakeup = ppp_asynctty_wakeup, }; static int __init ppp_async_init(void) { int err; err = tty_register_ldisc(&ppp_ldisc); if (err != 0) printk(KERN_ERR "PPP_async: error %d registering line disc.\n", err); return err; } /* * The following routines provide the PPP channel interface. */ static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg) { struct asyncppp *ap = chan->private; void __user *argp = (void __user *)arg; int __user *p = argp; int err, val; u32 accm[8]; err = -EFAULT; switch (cmd) { case PPPIOCGFLAGS: val = ap->flags | ap->rbits; if (put_user(val, p)) break; err = 0; break; case PPPIOCSFLAGS: if (get_user(val, p)) break; ap->flags = val & ~SC_RCV_BITS; spin_lock_irq(&ap->recv_lock); ap->rbits = val & SC_RCV_BITS; spin_unlock_irq(&ap->recv_lock); err = 0; break; case PPPIOCGASYNCMAP: if (put_user(ap->xaccm[0], (u32 __user *)argp)) break; err = 0; break; case PPPIOCSASYNCMAP: if (get_user(ap->xaccm[0], (u32 __user *)argp)) break; err = 0; break; case PPPIOCGRASYNCMAP: if (put_user(ap->raccm, (u32 __user *)argp)) break; err = 0; break; case PPPIOCSRASYNCMAP: if (get_user(ap->raccm, (u32 __user *)argp)) break; err = 0; break; case PPPIOCGXASYNCMAP: if (copy_to_user(argp, ap->xaccm, sizeof(ap->xaccm))) break; err = 0; break; case PPPIOCSXASYNCMAP: if (copy_from_user(accm, argp, sizeof(accm))) break; accm[2] &= ~0x40000000U; /* can't escape 0x5e */ accm[3] |= 0x60000000U; /* must escape 0x7d, 0x7e */ memcpy(ap->xaccm, accm, sizeof(ap->xaccm)); err = 0; break; case PPPIOCGMRU: if (put_user(ap->mru, p)) break; err = 0; break; case PPPIOCSMRU: if (get_user(val, p)) break; if (val > U16_MAX) { err = -EINVAL; break; } if (val < PPP_MRU) val = PPP_MRU; ap->mru = val; err = 0; break; default: err = -ENOTTY; } return err; } /* * This is called at softirq level to deliver received packets * to the ppp_generic code, and to tell the ppp_generic code * if we can accept more output now. */ static void ppp_async_process(struct tasklet_struct *t) { struct asyncppp *ap = from_tasklet(ap, t, tsk); struct sk_buff *skb; /* process received packets */ while ((skb = skb_dequeue(&ap->rqueue)) != NULL) { if (skb->cb[0]) ppp_input_error(&ap->chan, 0); ppp_input(&ap->chan, skb); } /* try to push more stuff out */ if (test_bit(XMIT_WAKEUP, &ap->xmit_flags) && ppp_async_push(ap)) ppp_output_wakeup(&ap->chan); } /* * Procedures for encapsulation and framing. */ /* * Procedure to encode the data for async serial transmission. * Does octet stuffing (escaping), puts the address/control bytes * on if A/C compression is disabled, and does protocol compression. * Assumes ap->tpkt != 0 on entry. * Returns 1 if we finished the current frame, 0 otherwise. */ #define PUT_BYTE(ap, buf, c, islcp) do { \ if ((islcp && c < 0x20) || (ap->xaccm[c >> 5] & (1 << (c & 0x1f)))) {\ *buf++ = PPP_ESCAPE; \ *buf++ = c ^ PPP_TRANS; \ } else \ *buf++ = c; \ } while (0) static int ppp_async_encode(struct asyncppp *ap) { int fcs, i, count, c, proto; unsigned char *buf, *buflim; unsigned char *data; int islcp; buf = ap->obuf; ap->olim = buf; ap->optr = buf; i = ap->tpkt_pos; data = ap->tpkt->data; count = ap->tpkt->len; fcs = ap->tfcs; proto = get_unaligned_be16(data); /* * LCP packets with code values between 1 (configure-request) * and 7 (code-reject) must be sent as though no options * had been negotiated. */ islcp = proto == PPP_LCP && count >= 3 && 1 <= data[2] && data[2] <= 7; if (i == 0) { if (islcp) async_lcp_peek(ap, data, count, 0); /* * Start of a new packet - insert the leading FLAG * character if necessary. */ if (islcp || flag_time == 0 || time_after_eq(jiffies, ap->last_xmit + flag_time)) *buf++ = PPP_FLAG; ap->last_xmit = jiffies; fcs = PPP_INITFCS; /* * Put in the address/control bytes if necessary */ if ((ap->flags & SC_COMP_AC) == 0 || islcp) { PUT_BYTE(ap, buf, 0xff, islcp); fcs = PPP_FCS(fcs, 0xff); PUT_BYTE(ap, buf, 0x03, islcp); fcs = PPP_FCS(fcs, 0x03); } } /* * Once we put in the last byte, we need to put in the FCS * and closing flag, so make sure there is at least 7 bytes * of free space in the output buffer. */ buflim = ap->obuf + OBUFSIZE - 6; while (i < count && buf < buflim) { c = data[i++]; if (i == 1 && c == 0 && (ap->flags & SC_COMP_PROT)) continue; /* compress protocol field */ fcs = PPP_FCS(fcs, c); PUT_BYTE(ap, buf, c, islcp); } if (i < count) { /* * Remember where we are up to in this packet. */ ap->olim = buf; ap->tpkt_pos = i; ap->tfcs = fcs; return 0; } /* * We have finished the packet. Add the FCS and flag. */ fcs = ~fcs; c = fcs & 0xff; PUT_BYTE(ap, buf, c, islcp); c = (fcs >> 8) & 0xff; PUT_BYTE(ap, buf, c, islcp); *buf++ = PPP_FLAG; ap->olim = buf; consume_skb(ap->tpkt); ap->tpkt = NULL; return 1; } /* * Transmit-side routines. */ /* * Send a packet to the peer over an async tty line. * Returns 1 iff the packet was accepted. * If the packet was not accepted, we will call ppp_output_wakeup * at some later time. */ static int ppp_async_send(struct ppp_channel *chan, struct sk_buff *skb) { struct asyncppp *ap = chan->private; ppp_async_push(ap); if (test_and_set_bit(XMIT_FULL, &ap->xmit_flags)) return 0; /* already full */ ap->tpkt = skb; ap->tpkt_pos = 0; ppp_async_push(ap); return 1; } /* * Push as much data as possible out to the tty. */ static int ppp_async_push(struct asyncppp *ap) { int avail, sent, done = 0; struct tty_struct *tty = ap->tty; int tty_stuffed = 0; /* * We can get called recursively here if the tty write * function calls our wakeup function. This can happen * for example on a pty with both the master and slave * set to PPP line discipline. * We use the XMIT_BUSY bit to detect this and get out, * leaving the XMIT_WAKEUP bit set to tell the other * instance that it may now be able to write more now. */ if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags)) return 0; spin_lock_bh(&ap->xmit_lock); for (;;) { if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags)) tty_stuffed = 0; if (!tty_stuffed && ap->optr < ap->olim) { avail = ap->olim - ap->optr; set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); sent = tty->ops->write(tty, ap->optr, avail); if (sent < 0) goto flush; /* error, e.g. loss of CD */ ap->optr += sent; if (sent < avail) tty_stuffed = 1; continue; } if (ap->optr >= ap->olim && ap->tpkt) { if (ppp_async_encode(ap)) { /* finished processing ap->tpkt */ clear_bit(XMIT_FULL, &ap->xmit_flags); done = 1; } continue; } /* * We haven't made any progress this time around. * Clear XMIT_BUSY to let other callers in, but * after doing so we have to check if anyone set * XMIT_WAKEUP since we last checked it. If they * did, we should try again to set XMIT_BUSY and go * around again in case XMIT_BUSY was still set when * the other caller tried. */ clear_bit(XMIT_BUSY, &ap->xmit_flags); /* any more work to do? if not, exit the loop */ if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags) || (!tty_stuffed && ap->tpkt))) break; /* more work to do, see if we can do it now */ if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags)) break; } spin_unlock_bh(&ap->xmit_lock); return done; flush: clear_bit(XMIT_BUSY, &ap->xmit_flags); if (ap->tpkt) { kfree_skb(ap->tpkt); ap->tpkt = NULL; clear_bit(XMIT_FULL, &ap->xmit_flags); done = 1; } ap->optr = ap->olim; spin_unlock_bh(&ap->xmit_lock); return done; } /* * Flush output from our internal buffers. * Called for the TCFLSH ioctl. Can be entered in parallel * but this is covered by the xmit_lock. */ static void ppp_async_flush_output(struct asyncppp *ap) { int done = 0; spin_lock_bh(&ap->xmit_lock); ap->optr = ap->olim; if (ap->tpkt != NULL) { kfree_skb(ap->tpkt); ap->tpkt = NULL; clear_bit(XMIT_FULL, &ap->xmit_flags); done = 1; } spin_unlock_bh(&ap->xmit_lock); if (done) ppp_output_wakeup(&ap->chan); } /* * Receive-side routines. */ /* see how many ordinary chars there are at the start of buf */ static inline int scan_ordinary(struct asyncppp *ap, const unsigned char *buf, int count) { int i, c; for (i = 0; i < count; ++i) { c = buf[i]; if (c == PPP_ESCAPE || c == PPP_FLAG || (c < 0x20 && (ap->raccm & (1 << c)) != 0)) break; } return i; } /* called when a flag is seen - do end-of-packet processing */ static void process_input_packet(struct asyncppp *ap) { struct sk_buff *skb; unsigned char *p; unsigned int len, fcs; skb = ap->rpkt; if (ap->state & (SC_TOSS | SC_ESCAPE)) goto err; if (skb == NULL) return; /* 0-length packet */ /* check the FCS */ p = skb->data; len = skb->len; if (len < 3) goto err; /* too short */ fcs = PPP_INITFCS; for (; len > 0; --len) fcs = PPP_FCS(fcs, *p++); if (fcs != PPP_GOODFCS) goto err; /* bad FCS */ skb_trim(skb, skb->len - 2); /* check for address/control and protocol compression */ p = skb->data; if (p[0] == PPP_ALLSTATIONS) { /* chop off address/control */ if (p[1] != PPP_UI || skb->len < 3) goto err; p = skb_pull(skb, 2); } /* If protocol field is not compressed, it can be LCP packet */ if (!(p[0] & 0x01)) { unsigned int proto; if (skb->len < 2) goto err; proto = (p[0] << 8) + p[1]; if (proto == PPP_LCP) async_lcp_peek(ap, p, skb->len, 1); } /* queue the frame to be processed */ skb->cb[0] = ap->state; skb_queue_tail(&ap->rqueue, skb); ap->rpkt = NULL; ap->state = 0; return; err: /* frame had an error, remember that, reset SC_TOSS & SC_ESCAPE */ ap->state = SC_PREV_ERROR; if (skb) { /* make skb appear as freshly allocated */ skb_trim(skb, 0); skb_reserve(skb, - skb_headroom(skb)); } } /* Called when the tty driver has data for us. Runs parallel with the other ldisc functions but will not be re-entered */ static void ppp_async_input(struct asyncppp *ap, const u8 *buf, const u8 *flags, int count) { struct sk_buff *skb; int c, i, j, n, s, f; unsigned char *sp; /* update bits used for 8-bit cleanness detection */ if (~ap->rbits & SC_RCV_BITS) { s = 0; for (i = 0; i < count; ++i) { c = buf[i]; if (flags && flags[i] != 0) continue; s |= (c & 0x80)? SC_RCV_B7_1: SC_RCV_B7_0; c = ((c >> 4) ^ c) & 0xf; s |= (0x6996 & (1 << c))? SC_RCV_ODDP: SC_RCV_EVNP; } ap->rbits |= s; } while (count > 0) { /* scan through and see how many chars we can do in bulk */ if ((ap->state & SC_ESCAPE) && buf[0] == PPP_ESCAPE) n = 1; else n = scan_ordinary(ap, buf, count); f = 0; if (flags && (ap->state & SC_TOSS) == 0) { /* check the flags to see if any char had an error */ for (j = 0; j < n; ++j) if ((f = flags[j]) != 0) break; } if (f != 0) { /* start tossing */ ap->state |= SC_TOSS; } else if (n > 0 && (ap->state & SC_TOSS) == 0) { /* stuff the chars in the skb */ skb = ap->rpkt; if (!skb) { skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2); if (!skb) goto nomem; ap->rpkt = skb; } if (skb->len == 0) { /* Try to get the payload 4-byte aligned. * This should match the * PPP_ALLSTATIONS/PPP_UI/compressed tests in * process_input_packet, but we do not have * enough chars here to test buf[1] and buf[2]. */ if (buf[0] != PPP_ALLSTATIONS) skb_reserve(skb, 2 + (buf[0] & 1)); } if (n > skb_tailroom(skb)) { /* packet overflowed MRU */ ap->state |= SC_TOSS; } else { sp = skb_put_data(skb, buf, n); if (ap->state & SC_ESCAPE) { sp[0] ^= PPP_TRANS; ap->state &= ~SC_ESCAPE; } } } if (n >= count) break; c = buf[n]; if (flags != NULL && flags[n] != 0) { ap->state |= SC_TOSS; } else if (c == PPP_FLAG) { process_input_packet(ap); } else if (c == PPP_ESCAPE) { ap->state |= SC_ESCAPE; } else if (I_IXON(ap->tty)) { if (c == START_CHAR(ap->tty)) start_tty(ap->tty); else if (c == STOP_CHAR(ap->tty)) stop_tty(ap->tty); } /* otherwise it's a char in the recv ACCM */ ++n; buf += n; if (flags) flags += n; count -= n; } return; nomem: printk(KERN_ERR "PPPasync: no memory (input pkt)\n"); ap->state |= SC_TOSS; } /* * We look at LCP frames going past so that we can notice * and react to the LCP configure-ack from the peer. * In the situation where the peer has been sent a configure-ack * already, LCP is up once it has sent its configure-ack * so the immediately following packet can be sent with the * configured LCP options. This allows us to process the following * packet correctly without pppd needing to respond quickly. * * We only respond to the received configure-ack if we have just * sent a configure-request, and the configure-ack contains the * same data (this is checked using a 16-bit crc of the data). */ #define CONFREQ 1 /* LCP code field values */ #define CONFACK 2 #define LCP_MRU 1 /* LCP option numbers */ #define LCP_ASYNCMAP 2 static void async_lcp_peek(struct asyncppp *ap, unsigned char *data, int len, int inbound) { int dlen, fcs, i, code; u32 val; data += 2; /* skip protocol bytes */ len -= 2; if (len < 4) /* 4 = code, ID, length */ return; code = data[0]; if (code != CONFACK && code != CONFREQ) return; dlen = get_unaligned_be16(data + 2); if (len < dlen) return; /* packet got truncated or length is bogus */ if (code == (inbound? CONFACK: CONFREQ)) { /* * sent confreq or received confack: * calculate the crc of the data from the ID field on. */ fcs = PPP_INITFCS; for (i = 1; i < dlen; ++i) fcs = PPP_FCS(fcs, data[i]); if (!inbound) { /* outbound confreq - remember the crc for later */ ap->lcp_fcs = fcs; return; } /* received confack, check the crc */ fcs ^= ap->lcp_fcs; ap->lcp_fcs = -1; if (fcs != 0) return; } else if (inbound) return; /* not interested in received confreq */ /* process the options in the confack */ data += 4; dlen -= 4; /* data[0] is code, data[1] is length */ while (dlen >= 2 && dlen >= data[1] && data[1] >= 2) { switch (data[0]) { case LCP_MRU: val = get_unaligned_be16(data + 2); if (inbound) ap->mru = val; else ap->chan.mtu = val; break; case LCP_ASYNCMAP: val = get_unaligned_be32(data + 2); if (inbound) ap->raccm = val; else ap->xaccm[0] = val; break; } dlen -= data[1]; data += data[1]; } } static void __exit ppp_async_cleanup(void) { tty_unregister_ldisc(&ppp_ldisc); } module_init(ppp_async_init); module_exit(ppp_async_cleanup);