/* * PPP async serial channel driver for Linux. * * Copyright 1999 Paul Mackerras. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. * * 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. * * ==FILEVERSION 20000227== */ #include #include #include #include #include #include #include #include #include #include #include #include #define PPP_VERSION "2.4.1" #define OBUFSIZE 256 /* 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 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 0x20000000 #define SC_ESCAPE 0x40000000 /* 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_PARM(flag_time, "i"); MODULE_PARM_DESC(flag_time, "ppp_async: interval between flagged packets (in clock ticks)"); MODULE_LICENSE("GPL"); /* * 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, char *flags, int count); static int ppp_async_ioctl(struct ppp_channel *chan, unsigned int cmd, unsigned long arg); static void async_lcp_peek(struct asyncppp *ap, unsigned char *data, int len, int inbound); static struct ppp_channel_ops async_ops = { ppp_async_send, ppp_async_ioctl }; /* * Routines implementing the PPP line discipline. */ /* * Called when a tty is put into PPP line discipline. */ static int ppp_asynctty_open(struct tty_struct *tty) { struct asyncppp *ap; int err; MOD_INC_USE_COUNT; err = -ENOMEM; ap = kmalloc(sizeof(*ap), GFP_KERNEL); if (ap == 0) goto out; /* initialize the asyncppp structure */ memset(ap, 0, sizeof(*ap)); 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; ap->chan.private = ap; ap->chan.ops = &async_ops; ap->chan.mtu = PPP_MRU; err = ppp_register_channel(&ap->chan); if (err) goto out_free; tty->disc_data = ap; return 0; out_free: kfree(ap); out: MOD_DEC_USE_COUNT; return err; } /* * Called when the tty is put into another line discipline * or it hangs up. * We assume that while we are in this routine, the tty layer * won't call any of the other line discipline entries for the * same tty. */ static void ppp_asynctty_close(struct tty_struct *tty) { struct asyncppp *ap = tty->disc_data; if (ap == 0) return; tty->disc_data = 0; ppp_unregister_channel(&ap->chan); if (ap->rpkt != 0) kfree_skb(ap->rpkt); if (ap->tpkt != 0) kfree_skb(ap->tpkt); kfree(ap); MOD_DEC_USE_COUNT; } /* * 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, unsigned char *buf, size_t count) { 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 unsigned char *buf, size_t count) { return -EAGAIN; } static int ppp_asynctty_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg) { struct asyncppp *ap = tty->disc_data; int err, val; err = -EFAULT; switch (cmd) { case PPPIOCGCHAN: err = -ENXIO; if (ap == 0) break; err = -EFAULT; if (put_user(ppp_channel_index(&ap->chan), (int *) arg)) break; err = 0; break; case PPPIOCGUNIT: err = -ENXIO; if (ap == 0) break; err = -EFAULT; if (put_user(ppp_unit_number(&ap->chan), (int *) arg)) break; err = 0; break; case TCGETS: case TCGETA: err = n_tty_ioctl(tty, file, cmd, arg); 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(tty, file, cmd, arg); break; case FIONREAD: val = 0; if (put_user(val, (int *) arg)) break; err = 0; break; default: err = -ENOIOCTLCMD; } return err; } /* No kernel lock - fine */ static unsigned int ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait) { return 0; } static int ppp_asynctty_room(struct tty_struct *tty) { return 65535; } static void ppp_asynctty_receive(struct tty_struct *tty, const unsigned char *buf, char *flags, int count) { struct asyncppp *ap = tty->disc_data; if (ap == 0) return; spin_lock_bh(&ap->recv_lock); ppp_async_input(ap, buf, flags, count); spin_unlock_bh(&ap->recv_lock); if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) && tty->driver.unthrottle) tty->driver.unthrottle(tty); } static void ppp_asynctty_wakeup(struct tty_struct *tty) { struct asyncppp *ap = tty->disc_data; clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); if (ap == 0) return; if (ppp_async_push(ap)) ppp_output_wakeup(&ap->chan); } static struct tty_ldisc ppp_ldisc = { magic: TTY_LDISC_MAGIC, name: "ppp", open: ppp_asynctty_open, close: ppp_asynctty_close, read: ppp_asynctty_read, write: ppp_asynctty_write, ioctl: ppp_asynctty_ioctl, poll: ppp_asynctty_poll, receive_room: ppp_asynctty_room, receive_buf: ppp_asynctty_receive, write_wakeup: ppp_asynctty_wakeup, }; static int __init ppp_async_init(void) { int err; err = tty_register_ldisc(N_PPP, &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; int err, val; u32 accm[8]; err = -EFAULT; switch (cmd) { case PPPIOCGFLAGS: val = ap->flags | ap->rbits; if (put_user(val, (int *) arg)) break; err = 0; break; case PPPIOCSFLAGS: if (get_user(val, (int *) arg)) break; ap->flags = val & ~SC_RCV_BITS; spin_lock_bh(&ap->recv_lock); ap->rbits = val & SC_RCV_BITS; spin_unlock_bh(&ap->recv_lock); err = 0; break; case PPPIOCGASYNCMAP: if (put_user(ap->xaccm[0], (u32 *) arg)) break; err = 0; break; case PPPIOCSASYNCMAP: if (get_user(ap->xaccm[0], (u32 *) arg)) break; err = 0; break; case PPPIOCGRASYNCMAP: if (put_user(ap->raccm, (u32 *) arg)) break; err = 0; break; case PPPIOCSRASYNCMAP: if (get_user(ap->raccm, (u32 *) arg)) break; err = 0; break; case PPPIOCGXASYNCMAP: if (copy_to_user((void *) arg, ap->xaccm, sizeof(ap->xaccm))) break; err = 0; break; case PPPIOCSXASYNCMAP: if (copy_from_user(accm, (void *) arg, 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, (int *) arg)) break; err = 0; break; case PPPIOCSMRU: if (get_user(val, (int *) arg)) break; if (val < PPP_MRU) val = PPP_MRU; ap->mru = val; err = 0; break; default: err = -ENOTTY; } return err; } /* * Procedures for encapsulation and framing. */ u16 ppp_crc16_table[256] = { 0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf, 0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7, 0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e, 0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876, 0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd, 0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5, 0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c, 0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974, 0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb, 0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3, 0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a, 0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72, 0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9, 0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1, 0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738, 0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70, 0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7, 0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff, 0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036, 0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e, 0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5, 0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd, 0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134, 0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c, 0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3, 0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb, 0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232, 0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a, 0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1, 0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9, 0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330, 0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78 }; EXPORT_SYMBOL(ppp_crc16_table); #define fcstab ppp_crc16_table /* for PPP_FCS macro */ /* * 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 ^ 0x20; \ } 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 = (data[0] << 8) + data[1]; /* * LCP packets with code values between 1 (configure-reqest) * and 7 (code-reject) must be sent as though no options * had been negotiated. */ islcp = proto == PPP_LCP && 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 || 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; kfree_skb(ap->tpkt); ap->tpkt = 0; 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; set_bit(XMIT_WAKEUP, &ap->xmit_flags); /* * 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->driver.write(tty, 0, 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 != 0) { 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 != 0))) 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 != 0) { kfree_skb(ap->tpkt); ap->tpkt = 0; 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. */ 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 = 0; 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 inline void process_input_packet(struct asyncppp *ap) { struct sk_buff *skb; unsigned char *p; unsigned int len, fcs, proto; int code = 0; skb = ap->rpkt; ap->rpkt = 0; if ((ap->state & (SC_TOSS | SC_ESCAPE)) || skb == 0) { ap->state &= ~(SC_TOSS | SC_ESCAPE); if (skb != 0) kfree_skb(skb); return; } /* 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 && p[1] == PPP_UI) { /* chop off address/control */ if (skb->len < 3) goto err; p = skb_pull(skb, 2); } proto = p[0]; if (proto & 1) { /* protocol is compressed */ skb_push(skb, 1)[0] = 0; } else { if (skb->len < 2) goto err; proto = (proto << 8) + p[1]; if (proto == PPP_LCP) async_lcp_peek(ap, p, skb->len, 1); } /* all OK, give it to the generic layer */ ppp_input(&ap->chan, skb); return; err: kfree_skb(skb); ppp_input_error(&ap->chan, code); } static inline void input_error(struct asyncppp *ap, int code) { ap->state |= SC_TOSS; ppp_input_error(&ap->chan, code); } /* called when the tty driver has data for us. */ static void ppp_async_input(struct asyncppp *ap, const unsigned char *buf, char *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 != 0 && 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 != 0 && (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 */ input_error(ap, f); } else if (n > 0 && (ap->state & SC_TOSS) == 0) { /* stuff the chars in the skb */ skb = ap->rpkt; if (skb == 0) { skb = dev_alloc_skb(ap->mru + PPP_HDRLEN + 2); if (skb == 0) goto nomem; /* Try to get the payload 4-byte aligned */ if (buf[0] != PPP_ALLSTATIONS) skb_reserve(skb, 2 + (buf[0] & 1)); ap->rpkt = skb; } if (n > skb_tailroom(skb)) { /* packet overflowed MRU */ input_error(ap, 1); } else { sp = skb_put(skb, n); memcpy(sp, buf, n); if (ap->state & SC_ESCAPE) { sp[0] ^= 0x20; ap->state &= ~SC_ESCAPE; } } } if (n >= count) break; c = buf[n]; if (c == PPP_FLAG) { process_input_packet(ap); } else if (c == PPP_ESCAPE) { ap->state |= SC_ESCAPE; } /* otherwise it's a char in the recv ACCM */ ++n; buf += n; if (flags != 0) flags += n; count -= n; } return; nomem: printk(KERN_ERR "PPPasync: no memory (input pkt)\n"); input_error(ap, 0); } /* * 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 = (data[2] << 8) + data[3]; 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]) { switch (data[0]) { case LCP_MRU: val = (data[2] << 8) + data[3]; if (inbound) ap->mru = val; else ap->chan.mtu = val; break; case LCP_ASYNCMAP: val = (data[2] << 24) + (data[3] << 16) + (data[4] << 8) + data[5]; if (inbound) ap->raccm = val; else ap->xaccm[0] = val; break; } dlen -= data[1]; data += data[1]; } } static void __exit ppp_async_cleanup(void) { if (tty_register_ldisc(N_PPP, NULL) != 0) printk(KERN_ERR "failed to unregister PPP line discipline\n"); } module_init(ppp_async_init); module_exit(ppp_async_cleanup);