Fixed MTP to work with TWRP

drivers/net/slip/Kconfig

@@ -0,0 +1,80 @@
+#
+# SLIP network device configuration
+#
+
+config SLIP
+	tristate "SLIP (serial line) support"
+	depends on TTY
+	---help---
+	  Say Y if you intend to use SLIP or CSLIP (compressed SLIP) to
+	  connect to your Internet service provider or to connect to some
+	  other local Unix box or if you want to configure your Linux box as a
+	  Slip/CSlip server for other people to dial in. SLIP (Serial Line
+	  Internet Protocol) is a protocol used to send Internet traffic over
+	  serial connections such as telephone lines or null modem cables;
+	  nowadays, the protocol PPP is more commonly used for this same
+	  purpose.
+
+	  Normally, your access provider has to support SLIP in order for you
+	  to be able to use it, but there is now a SLIP emulator called SLiRP
+	  around (available from
+	  <ftp://ibiblio.org/pub/Linux/system/network/serial/>) which
+	  allows you to use SLIP over a regular dial up shell connection. If
+	  you plan to use SLiRP, make sure to say Y to CSLIP, below. The
+	  NET-3-HOWTO, available from
+	  <http://www.tldp.org/docs.html#howto>, explains how to
+	  configure SLIP. Note that you don't need this option if you just
+	  want to run term (term is a program which gives you almost full
+	  Internet connectivity if you have a regular dial up shell account on
+	  some Internet connected Unix computer. Read
+	  <http://www.bart.nl/~patrickr/term-howto/Term-HOWTO.html>). SLIP
+	  support will enlarge your kernel by about 4 KB. If unsure, say N.
+
+	  To compile this driver as a module, choose M here. The module
+	  will be called slip.
+
+config SLHC
+	tristate
+	---help---
+	  This option enables Van Jacobsen serial line header compression
+	  routines.
+
+if SLIP
+
+config SLIP_COMPRESSED
+	bool "CSLIP compressed headers"
+	depends on SLIP
+	select SLHC
+	---help---
+	  This protocol is faster than SLIP because it uses compression on the
+	  TCP/IP headers (not on the data itself), but it has to be supported
+	  on both ends. Ask your access provider if you are not sure and
+	  answer Y, just in case. You will still be able to use plain SLIP. If
+	  you plan to use SLiRP, the SLIP emulator (available from
+	  <ftp://ibiblio.org/pub/Linux/system/network/serial/>) which
+	  allows you to use SLIP over a regular dial up shell connection, you
+	  definitely want to say Y here. The NET-3-HOWTO, available from
+	  <http://www.tldp.org/docs.html#howto>, explains how to configure
+	  CSLIP. This won't enlarge your kernel.
+
+config SLIP_SMART
+	bool "Keepalive and linefill"
+	depends on SLIP
+	---help---
+	  Adds additional capabilities to the SLIP driver to support the
+	  RELCOM line fill and keepalive monitoring. Ideal on poor quality
+	  analogue lines.
+
+config SLIP_MODE_SLIP6
+	bool "Six bit SLIP encapsulation"
+	depends on SLIP
+	---help---
+	  Just occasionally you may need to run IP over hostile serial
+	  networks that don't pass all control characters or are only seven
+	  bit. Saying Y here adds an extra mode you can use with SLIP:
+	  "slip6". In this mode, SLIP will only send normal ASCII symbols over
+	  the serial device. Naturally, this has to be supported at the other
+	  end of the link as well. It's good enough, for example, to run IP
+	  over the async ports of a Camtec JNT Pad. If unsure, say N.
+
+endif # SLIP

drivers/net/slip/Makefile

@@ -0,0 +1,6 @@
+#
+# Makefile for the SLIP network device drivers.
+#
+
+obj-$(CONFIG_SLIP) += slip.o
+obj-$(CONFIG_SLHC) += slhc.o

drivers/net/slip/slhc.c

@@ -0,0 +1,740 @@
+/*
+ * Routines to compress and uncompress tcp packets (for transmission
+ * over low speed serial lines).
+ *
+ * Copyright (c) 1989 Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms are permitted
+ * provided that the above copyright notice and this paragraph are
+ * duplicated in all such forms and that any documentation,
+ * advertising materials, and other materials related to such
+ * distribution and use acknowledge that the software was developed
+ * by the University of California, Berkeley.  The name of the
+ * University may not be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ *	Van Jacobson (van@helios.ee.lbl.gov), Dec 31, 1989:
+ *	- Initial distribution.
+ *
+ *
+ * modified for KA9Q Internet Software Package by
+ * Katie Stevens (dkstevens@ucdavis.edu)
+ * University of California, Davis
+ * Computing Services
+ *	- 01-31-90	initial adaptation (from 1.19)
+ *	PPP.05	02-15-90 [ks]
+ *	PPP.08	05-02-90 [ks]	use PPP protocol field to signal compression
+ *	PPP.15	09-90	 [ks]	improve mbuf handling
+ *	PPP.16	11-02	 [karn]	substantially rewritten to use NOS facilities
+ *
+ *	- Feb 1991	Bill_Simpson@um.cc.umich.edu
+ *			variable number of conversation slots
+ *			allow zero or one slots
+ *			separate routines
+ *			status display
+ *	- Jul 1994	Dmitry Gorodchanin
+ *			Fixes for memory leaks.
+ *      - Oct 1994      Dmitry Gorodchanin
+ *                      Modularization.
+ *	- Jan 1995	Bjorn Ekwall
+ *			Use ip_fast_csum from ip.h
+ *	- July 1995	Christos A. Polyzols
+ *			Spotted bug in tcp option checking
+ *
+ *
+ *	This module is a difficult issue. It's clearly inet code but it's also clearly
+ *	driver code belonging close to PPP and SLIP
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <net/slhc_vj.h>
+
+#ifdef CONFIG_INET
+/* Entire module is for IP only */
+#include <linux/mm.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/termios.h>
+#include <linux/in.h>
+#include <linux/fcntl.h>
+#include <linux/inet.h>
+#include <linux/netdevice.h>
+#include <net/ip.h>
+#include <net/protocol.h>
+#include <net/icmp.h>
+#include <net/tcp.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <linux/timer.h>
+#include <asm/uaccess.h>
+#include <net/checksum.h>
+#include <asm/unaligned.h>
+
+static unsigned char *encode(unsigned char *cp, unsigned short n);
+static long decode(unsigned char **cpp);
+static unsigned char * put16(unsigned char *cp, unsigned short x);
+static unsigned short pull16(unsigned char **cpp);
+
+/* Initialize compression data structure
+ *	slots must be in range 0 to 255 (zero meaning no compression)
+ */
+struct slcompress *
+slhc_init(int rslots, int tslots)
+{
+	register short i;
+	register struct cstate *ts;
+	struct slcompress *comp;
+
+	comp = kzalloc(sizeof(struct slcompress), GFP_KERNEL);
+	if (! comp)
+		goto out_fail;
+
+	if ( rslots > 0  &&  rslots < 256 ) {
+		size_t rsize = rslots * sizeof(struct cstate);
+		comp->rstate = kzalloc(rsize, GFP_KERNEL);
+		if (! comp->rstate)
+			goto out_free;
+		comp->rslot_limit = rslots - 1;
+	}
+
+	if ( tslots > 0  &&  tslots < 256 ) {
+		size_t tsize = tslots * sizeof(struct cstate);
+		comp->tstate = kzalloc(tsize, GFP_KERNEL);
+		if (! comp->tstate)
+			goto out_free2;
+		comp->tslot_limit = tslots - 1;
+	}
+
+	comp->xmit_oldest = 0;
+	comp->xmit_current = 255;
+	comp->recv_current = 255;
+	/*
+	 * don't accept any packets with implicit index until we get
+	 * one with an explicit index.  Otherwise the uncompress code
+	 * will try to use connection 255, which is almost certainly
+	 * out of range
+	 */
+	comp->flags |= SLF_TOSS;
+
+	if ( tslots > 0 ) {
+		ts = comp->tstate;
+		for(i = comp->tslot_limit; i > 0; --i){
+			ts[i].cs_this = i;
+			ts[i].next = &(ts[i - 1]);
+		}
+		ts[0].next = &(ts[comp->tslot_limit]);
+		ts[0].cs_this = 0;
+	}
+	return comp;
+
+out_free2:
+	kfree(comp->rstate);
+out_free:
+	kfree(comp);
+out_fail:
+	return NULL;
+}
+
+
+/* Free a compression data structure */
+void
+slhc_free(struct slcompress *comp)
+{
+	if ( comp == NULLSLCOMPR )
+		return;
+
+	if ( comp->tstate != NULLSLSTATE )
+		kfree( comp->tstate );
+
+	if ( comp->rstate != NULLSLSTATE )
+		kfree( comp->rstate );
+
+	kfree( comp );
+}
+
+
+/* Put a short in host order into a char array in network order */
+static inline unsigned char *
+put16(unsigned char *cp, unsigned short x)
+{
+	*cp++ = x >> 8;
+	*cp++ = x;
+
+	return cp;
+}
+
+
+/* Encode a number */
+static unsigned char *
+encode(unsigned char *cp, unsigned short n)
+{
+	if(n >= 256 || n == 0){
+		*cp++ = 0;
+		cp = put16(cp,n);
+	} else {
+		*cp++ = n;
+	}
+	return cp;
+}
+
+/* Pull a 16-bit integer in host order from buffer in network byte order */
+static unsigned short
+pull16(unsigned char **cpp)
+{
+	short rval;
+
+	rval = *(*cpp)++;
+	rval <<= 8;
+	rval |= *(*cpp)++;
+	return rval;
+}
+
+/* Decode a number */
+static long
+decode(unsigned char **cpp)
+{
+	register int x;
+
+	x = *(*cpp)++;
+	if(x == 0){
+		return pull16(cpp) & 0xffff;	/* pull16 returns -1 on error */
+	} else {
+		return x & 0xff;		/* -1 if PULLCHAR returned error */
+	}
+}
+
+/*
+ * icp and isize are the original packet.
+ * ocp is a place to put a copy if necessary.
+ * cpp is initially a pointer to icp.  If the copy is used,
+ *    change it to ocp.
+ */
+
+int
+slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
+	unsigned char *ocp, unsigned char **cpp, int compress_cid)
+{
+	register struct cstate *ocs = &(comp->tstate[comp->xmit_oldest]);
+	register struct cstate *lcs = ocs;
+	register struct cstate *cs = lcs->next;
+	register unsigned long deltaS, deltaA;
+	register short changes = 0;
+	int hlen;
+	unsigned char new_seq[16];
+	register unsigned char *cp = new_seq;
+	struct iphdr *ip;
+	struct tcphdr *th, *oth;
+	__sum16 csum;
+
+
+	/*
+	 *	Don't play with runt packets.
+	 */
+
+	if(isize<sizeof(struct iphdr))
+		return isize;
+
+	ip = (struct iphdr *) icp;
+
+	/* Bail if this packet isn't TCP, or is an IP fragment */
+	if (ip->protocol != IPPROTO_TCP || (ntohs(ip->frag_off) & 0x3fff)) {
+		/* Send as regular IP */
+		if(ip->protocol != IPPROTO_TCP)
+			comp->sls_o_nontcp++;
+		else
+			comp->sls_o_tcp++;
+		return isize;
+	}
+	/* Extract TCP header */
+
+	th = (struct tcphdr *)(((unsigned char *)ip) + ip->ihl*4);
+	hlen = ip->ihl*4 + th->doff*4;
+
+	/*  Bail if the TCP packet isn't `compressible' (i.e., ACK isn't set or
+	 *  some other control bit is set). Also uncompressible if
+	 *  it's a runt.
+	 */
+	if(hlen > isize || th->syn || th->fin || th->rst ||
+	    ! (th->ack)){
+		/* TCP connection stuff; send as regular IP */
+		comp->sls_o_tcp++;
+		return isize;
+	}
+	/*
+	 * Packet is compressible -- we're going to send either a
+	 * COMPRESSED_TCP or UNCOMPRESSED_TCP packet.  Either way,
+	 * we need to locate (or create) the connection state.
+	 *
+	 * States are kept in a circularly linked list with
+	 * xmit_oldest pointing to the end of the list.  The
+	 * list is kept in lru order by moving a state to the
+	 * head of the list whenever it is referenced.  Since
+	 * the list is short and, empirically, the connection
+	 * we want is almost always near the front, we locate
+	 * states via linear search.  If we don't find a state
+	 * for the datagram, the oldest state is (re-)used.
+	 */
+	for ( ; ; ) {
+		if( ip->saddr == cs->cs_ip.saddr
+		 && ip->daddr == cs->cs_ip.daddr
+		 && th->source == cs->cs_tcp.source
+		 && th->dest == cs->cs_tcp.dest)
+			goto found;
+
+		/* if current equal oldest, at end of list */
+		if ( cs == ocs )
+			break;
+		lcs = cs;
+		cs = cs->next;
+		comp->sls_o_searches++;
+	}
+	/*
+	 * Didn't find it -- re-use oldest cstate.  Send an
+	 * uncompressed packet that tells the other side what
+	 * connection number we're using for this conversation.
+	 *
+	 * Note that since the state list is circular, the oldest
+	 * state points to the newest and we only need to set
+	 * xmit_oldest to update the lru linkage.
+	 */
+	comp->sls_o_misses++;
+	comp->xmit_oldest = lcs->cs_this;
+	goto uncompressed;
+
+found:
+	/*
+	 * Found it -- move to the front on the connection list.
+	 */
+	if(lcs == ocs) {
+ 		/* found at most recently used */
+	} else if (cs == ocs) {
+		/* found at least recently used */
+		comp->xmit_oldest = lcs->cs_this;
+	} else {
+		/* more than 2 elements */
+		lcs->next = cs->next;
+		cs->next = ocs->next;
+		ocs->next = cs;
+	}
+
+	/*
+	 * Make sure that only what we expect to change changed.
+	 * Check the following:
+	 * IP protocol version, header length & type of service.
+	 * The "Don't fragment" bit.
+	 * The time-to-live field.
+	 * The TCP header length.
+	 * IP options, if any.
+	 * TCP options, if any.
+	 * If any of these things are different between the previous &
+	 * current datagram, we send the current datagram `uncompressed'.
+	 */
+	oth = &cs->cs_tcp;
+
+	if(ip->version != cs->cs_ip.version || ip->ihl != cs->cs_ip.ihl
+	 || ip->tos != cs->cs_ip.tos
+	 || (ip->frag_off & htons(0x4000)) != (cs->cs_ip.frag_off & htons(0x4000))
+	 || ip->ttl != cs->cs_ip.ttl
+	 || th->doff != cs->cs_tcp.doff
+	 || (ip->ihl > 5 && memcmp(ip+1,cs->cs_ipopt,((ip->ihl)-5)*4) != 0)
+	 || (th->doff > 5 && memcmp(th+1,cs->cs_tcpopt,((th->doff)-5)*4) != 0)){
+		goto uncompressed;
+	}
+
+	/*
+	 * Figure out which of the changing fields changed.  The
+	 * receiver expects changes in the order: urgent, window,
+	 * ack, seq (the order minimizes the number of temporaries
+	 * needed in this section of code).
+	 */
+	if(th->urg){
+		deltaS = ntohs(th->urg_ptr);
+		cp = encode(cp,deltaS);
+		changes |= NEW_U;
+	} else if(th->urg_ptr != oth->urg_ptr){
+		/* argh! URG not set but urp changed -- a sensible
+		 * implementation should never do this but RFC793
+		 * doesn't prohibit the change so we have to deal
+		 * with it. */
+		goto uncompressed;
+	}
+	if((deltaS = ntohs(th->window) - ntohs(oth->window)) != 0){
+		cp = encode(cp,deltaS);
+		changes |= NEW_W;
+	}
+	if((deltaA = ntohl(th->ack_seq) - ntohl(oth->ack_seq)) != 0L){
+		if(deltaA > 0x0000ffff)
+			goto uncompressed;
+		cp = encode(cp,deltaA);
+		changes |= NEW_A;
+	}
+	if((deltaS = ntohl(th->seq) - ntohl(oth->seq)) != 0L){
+		if(deltaS > 0x0000ffff)
+			goto uncompressed;
+		cp = encode(cp,deltaS);
+		changes |= NEW_S;
+	}
+
+	switch(changes){
+	case 0:	/* Nothing changed. If this packet contains data and the
+		 * last one didn't, this is probably a data packet following
+		 * an ack (normal on an interactive connection) and we send
+		 * it compressed.  Otherwise it's probably a retransmit,
+		 * retransmitted ack or window probe.  Send it uncompressed
+		 * in case the other side missed the compressed version.
+		 */
+		if(ip->tot_len != cs->cs_ip.tot_len &&
+		   ntohs(cs->cs_ip.tot_len) == hlen)
+			break;
+		goto uncompressed;
+	case SPECIAL_I:
+	case SPECIAL_D:
+		/* actual changes match one of our special case encodings --
+		 * send packet uncompressed.
+		 */
+		goto uncompressed;
+	case NEW_S|NEW_A:
+		if(deltaS == deltaA &&
+		    deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
+			/* special case for echoed terminal traffic */
+			changes = SPECIAL_I;
+			cp = new_seq;
+		}
+		break;
+	case NEW_S:
+		if(deltaS == ntohs(cs->cs_ip.tot_len) - hlen){
+			/* special case for data xfer */
+			changes = SPECIAL_D;
+			cp = new_seq;
+		}
+		break;
+	}
+	deltaS = ntohs(ip->id) - ntohs(cs->cs_ip.id);
+	if(deltaS != 1){
+		cp = encode(cp,deltaS);
+		changes |= NEW_I;
+	}
+	if(th->psh)
+		changes |= TCP_PUSH_BIT;
+	/* Grab the cksum before we overwrite it below.  Then update our
+	 * state with this packet's header.
+	 */
+	csum = th->check;
+	memcpy(&cs->cs_ip,ip,20);
+	memcpy(&cs->cs_tcp,th,20);
+	/* We want to use the original packet as our compressed packet.
+	 * (cp - new_seq) is the number of bytes we need for compressed
+	 * sequence numbers.  In addition we need one byte for the change
+	 * mask, one for the connection id and two for the tcp checksum.
+	 * So, (cp - new_seq) + 4 bytes of header are needed.
+	 */
+	deltaS = cp - new_seq;
+	if(compress_cid == 0 || comp->xmit_current != cs->cs_this){
+		cp = ocp;
+		*cpp = ocp;
+		*cp++ = changes | NEW_C;
+		*cp++ = cs->cs_this;
+		comp->xmit_current = cs->cs_this;
+	} else {
+		cp = ocp;
+		*cpp = ocp;
+		*cp++ = changes;
+	}
+	*(__sum16 *)cp = csum;
+	cp += 2;
+/* deltaS is now the size of the change section of the compressed header */
+	memcpy(cp,new_seq,deltaS);	/* Write list of deltas */
+	memcpy(cp+deltaS,icp+hlen,isize-hlen);
+	comp->sls_o_compressed++;
+	ocp[0] |= SL_TYPE_COMPRESSED_TCP;
+	return isize - hlen + deltaS + (cp - ocp);
+
+	/* Update connection state cs & send uncompressed packet (i.e.,
+	 * a regular ip/tcp packet but with the 'conversation id' we hope
+	 * to use on future compressed packets in the protocol field).
+	 */
+uncompressed:
+	memcpy(&cs->cs_ip,ip,20);
+	memcpy(&cs->cs_tcp,th,20);
+	if (ip->ihl > 5)
+	  memcpy(cs->cs_ipopt, ip+1, ((ip->ihl) - 5) * 4);
+	if (th->doff > 5)
+	  memcpy(cs->cs_tcpopt, th+1, ((th->doff) - 5) * 4);
+	comp->xmit_current = cs->cs_this;
+	comp->sls_o_uncompressed++;
+	memcpy(ocp, icp, isize);
+	*cpp = ocp;
+	ocp[9] = cs->cs_this;
+	ocp[0] |= SL_TYPE_UNCOMPRESSED_TCP;
+	return isize;
+}
+
+
+int
+slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
+{
+	register int changes;
+	long x;
+	register struct tcphdr *thp;
+	register struct iphdr *ip;
+	register struct cstate *cs;
+	int len, hdrlen;
+	unsigned char *cp = icp;
+
+	/* We've got a compressed packet; read the change byte */
+	comp->sls_i_compressed++;
+	if(isize < 3){
+		comp->sls_i_error++;
+		return 0;
+	}
+	changes = *cp++;
+	if(changes & NEW_C){
+		/* Make sure the state index is in range, then grab the state.
+		 * If we have a good state index, clear the 'discard' flag.
+		 */
+		x = *cp++;	/* Read conn index */
+		if(x < 0 || x > comp->rslot_limit)
+			goto bad;
+
+		comp->flags &=~ SLF_TOSS;
+		comp->recv_current = x;
+	} else {
+		/* this packet has an implicit state index.  If we've
+		 * had a line error since the last time we got an
+		 * explicit state index, we have to toss the packet. */
+		if(comp->flags & SLF_TOSS){
+			comp->sls_i_tossed++;
+			return 0;
+		}
+	}
+	cs = &comp->rstate[comp->recv_current];
+	thp = &cs->cs_tcp;
+	ip = &cs->cs_ip;
+
+	thp->check = *(__sum16 *)cp;
+	cp += 2;
+
+	thp->psh = (changes & TCP_PUSH_BIT) ? 1 : 0;
+/*
+ * we can use the same number for the length of the saved header and
+ * the current one, because the packet wouldn't have been sent
+ * as compressed unless the options were the same as the previous one
+ */
+
+	hdrlen = ip->ihl * 4 + thp->doff * 4;
+
+	switch(changes & SPECIALS_MASK){
+	case SPECIAL_I:		/* Echoed terminal traffic */
+		{
+		register short i;
+		i = ntohs(ip->tot_len) - hdrlen;
+		thp->ack_seq = htonl( ntohl(thp->ack_seq) + i);
+		thp->seq = htonl( ntohl(thp->seq) + i);
+		}
+		break;
+
+	case SPECIAL_D:			/* Unidirectional data */
+		thp->seq = htonl( ntohl(thp->seq) +
+				  ntohs(ip->tot_len) - hdrlen);
+		break;
+
+	default:
+		if(changes & NEW_U){
+			thp->urg = 1;
+			if((x = decode(&cp)) == -1) {
+				goto bad;
+			}
+			thp->urg_ptr = htons(x);
+		} else
+			thp->urg = 0;
+		if(changes & NEW_W){
+			if((x = decode(&cp)) == -1) {
+				goto bad;
+			}
+			thp->window = htons( ntohs(thp->window) + x);
+		}
+		if(changes & NEW_A){
+			if((x = decode(&cp)) == -1) {
+				goto bad;
+			}
+			thp->ack_seq = htonl( ntohl(thp->ack_seq) + x);
+		}
+		if(changes & NEW_S){
+			if((x = decode(&cp)) == -1) {
+				goto bad;
+			}
+			thp->seq = htonl( ntohl(thp->seq) + x);
+		}
+		break;
+	}
+	if(changes & NEW_I){
+		if((x = decode(&cp)) == -1) {
+			goto bad;
+		}
+		ip->id = htons (ntohs (ip->id) + x);
+	} else
+		ip->id = htons (ntohs (ip->id) + 1);
+
+	/*
+	 * At this point, cp points to the first byte of data in the
+	 * packet.  Put the reconstructed TCP and IP headers back on the
+	 * packet.  Recalculate IP checksum (but not TCP checksum).
+	 */
+
+	len = isize - (cp - icp);
+	if (len < 0)
+		goto bad;
+	len += hdrlen;
+	ip->tot_len = htons(len);
+	ip->check = 0;
+
+	memmove(icp + hdrlen, cp, len - hdrlen);
+
+	cp = icp;
+	memcpy(cp, ip, 20);
+	cp += 20;
+
+	if (ip->ihl > 5) {
+	  memcpy(cp, cs->cs_ipopt, (ip->ihl - 5) * 4);
+	  cp += (ip->ihl - 5) * 4;
+	}
+
+	put_unaligned(ip_fast_csum(icp, ip->ihl),
+		      &((struct iphdr *)icp)->check);
+
+	memcpy(cp, thp, 20);
+	cp += 20;
+
+	if (thp->doff > 5) {
+	  memcpy(cp, cs->cs_tcpopt, ((thp->doff) - 5) * 4);
+	  cp += ((thp->doff) - 5) * 4;
+	}
+
+	return len;
+bad:
+	comp->sls_i_error++;
+	return slhc_toss( comp );
+}
+
+
+int
+slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
+{
+	register struct cstate *cs;
+	unsigned ihl;
+
+	unsigned char index;
+
+	if(isize < 20) {
+		/* The packet is shorter than a legal IP header */
+		comp->sls_i_runt++;
+		return slhc_toss( comp );
+	}
+	/* Peek at the IP header's IHL field to find its length */
+	ihl = icp[0] & 0xf;
+	if(ihl < 20 / 4){
+		/* The IP header length field is too small */
+		comp->sls_i_runt++;
+		return slhc_toss( comp );
+	}
+	index = icp[9];
+	icp[9] = IPPROTO_TCP;
+
+	if (ip_fast_csum(icp, ihl)) {
+		/* Bad IP header checksum; discard */
+		comp->sls_i_badcheck++;
+		return slhc_toss( comp );
+	}
+	if(index > comp->rslot_limit) {
+		comp->sls_i_error++;
+		return slhc_toss(comp);
+	}
+
+	/* Update local state */
+	cs = &comp->rstate[comp->recv_current = index];
+	comp->flags &=~ SLF_TOSS;
+	memcpy(&cs->cs_ip,icp,20);
+	memcpy(&cs->cs_tcp,icp + ihl*4,20);
+	if (ihl > 5)
+	  memcpy(cs->cs_ipopt, icp + sizeof(struct iphdr), (ihl - 5) * 4);
+	if (cs->cs_tcp.doff > 5)
+	  memcpy(cs->cs_tcpopt, icp + ihl*4 + sizeof(struct tcphdr), (cs->cs_tcp.doff - 5) * 4);
+	cs->cs_hsize = ihl*2 + cs->cs_tcp.doff*2;
+	/* Put headers back on packet
+	 * Neither header checksum is recalculated
+	 */
+	comp->sls_i_uncompressed++;
+	return isize;
+}
+
+int
+slhc_toss(struct slcompress *comp)
+{
+	if ( comp == NULLSLCOMPR )
+		return 0;
+
+	comp->flags |= SLF_TOSS;
+	return 0;
+}
+
+#else /* CONFIG_INET */
+
+int
+slhc_toss(struct slcompress *comp)
+{
+  printk(KERN_DEBUG "Called IP function on non IP-system: slhc_toss");
+  return -EINVAL;
+}
+int
+slhc_uncompress(struct slcompress *comp, unsigned char *icp, int isize)
+{
+  printk(KERN_DEBUG "Called IP function on non IP-system: slhc_uncompress");
+  return -EINVAL;
+}
+int
+slhc_compress(struct slcompress *comp, unsigned char *icp, int isize,
+	unsigned char *ocp, unsigned char **cpp, int compress_cid)
+{
+  printk(KERN_DEBUG "Called IP function on non IP-system: slhc_compress");
+  return -EINVAL;
+}
+
+int
+slhc_remember(struct slcompress *comp, unsigned char *icp, int isize)
+{
+  printk(KERN_DEBUG "Called IP function on non IP-system: slhc_remember");
+  return -EINVAL;
+}
+
+void
+slhc_free(struct slcompress *comp)
+{
+  printk(KERN_DEBUG "Called IP function on non IP-system: slhc_free");
+}
+struct slcompress *
+slhc_init(int rslots, int tslots)
+{
+  printk(KERN_DEBUG "Called IP function on non IP-system: slhc_init");
+  return NULL;
+}
+
+#endif /* CONFIG_INET */
+
+/* VJ header compression */
+EXPORT_SYMBOL(slhc_init);
+EXPORT_SYMBOL(slhc_free);
+EXPORT_SYMBOL(slhc_remember);
+EXPORT_SYMBOL(slhc_compress);
+EXPORT_SYMBOL(slhc_uncompress);
+EXPORT_SYMBOL(slhc_toss);
+
+MODULE_LICENSE("Dual BSD/GPL");

drivers/net/slip/slip.h

@@ -0,0 +1,102 @@
+/*
+ * slip.h	Define the SLIP device driver interface and constants.
+ *
+ * NOTE:	THIS FILE WILL BE MOVED TO THE LINUX INCLUDE DIRECTORY
+ *		AS SOON AS POSSIBLE!
+ *
+ * Version:	@(#)slip.h	1.2.0	03/28/93
+ *
+ * Fixes:
+ *		Alan Cox	: 	Added slip mtu field.
+ *		Matt Dillon	:	Printable slip (borrowed from net2e)
+ *		Alan Cox	:	Added SL_SLIP_LOTS
+ *	Dmitry Gorodchanin	:	A lot of changes in the 'struct slip'
+ *	Dmitry Gorodchanin	:	Added CSLIP statistics.
+ *	Stanislav Voronyi	:	Make line checking as created by
+ *					Igor Chechik, RELCOM Corp.
+ *	Craig Schlenter		:	Fixed #define bug that caused
+ *					CSLIP telnets to hang in 1.3.61-6
+ *
+ * Author:	Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
+ */
+#ifndef _LINUX_SLIP_H
+#define _LINUX_SLIP_H
+
+
+#if defined(CONFIG_INET) && defined(CONFIG_SLIP_COMPRESSED)
+# define SL_INCLUDE_CSLIP
+#endif
+
+#ifdef SL_INCLUDE_CSLIP
+# define SL_MODE_DEFAULT SL_MODE_ADAPTIVE
+#else
+# define SL_MODE_DEFAULT SL_MODE_SLIP
+#endif
+
+/* SLIP configuration. */
+#define SL_NRUNIT	256		/* MAX number of SLIP channels;
+					   This can be overridden with
+					   insmod -oslip_maxdev=nnn	*/
+#define SL_MTU		296		/* 296; I am used to 600- FvK	*/
+
+/* SLIP protocol characters. */
+#define END             0300		/* indicates end of frame	*/
+#define ESC             0333		/* indicates byte stuffing	*/
+#define ESC_END         0334		/* ESC ESC_END means END 'data'	*/
+#define ESC_ESC         0335		/* ESC ESC_ESC means ESC 'data'	*/
+
+
+struct slip {
+  int			magic;
+
+  /* Various fields. */
+  struct tty_struct	*tty;		/* ptr to TTY structure		*/
+  struct net_device	*dev;		/* easy for intr handling	*/
+  spinlock_t		lock;
+  struct work_struct	tx_work;	/* Flushes transmit buffer	*/
+
+#ifdef SL_INCLUDE_CSLIP
+  struct slcompress	*slcomp;	/* for header compression 	*/
+  unsigned char		*cbuff;		/* compression buffer		*/
+#endif
+
+  /* These are pointers to the malloc()ed frame buffers. */
+  unsigned char		*rbuff;		/* receiver buffer		*/
+  int                   rcount;         /* received chars counter       */
+  unsigned char		*xbuff;		/* transmitter buffer		*/
+  unsigned char         *xhead;         /* pointer to next byte to XMIT */
+  int                   xleft;          /* bytes left in XMIT queue     */
+  int			mtu;		/* Our mtu (to spot changes!)   */
+  int                   buffsize;       /* Max buffers sizes            */
+
+#ifdef CONFIG_SLIP_MODE_SLIP6
+  int			xdata, xbits;	/* 6 bit slip controls 		*/
+#endif
+
+  unsigned long		flags;		/* Flag values/ mode etc	*/
+#define SLF_INUSE	0		/* Channel in use               */
+#define SLF_ESCAPE	1               /* ESC received                 */
+#define SLF_ERROR	2               /* Parity, etc. error           */
+#define SLF_KEEPTEST	3		/* Keepalive test flag		*/
+#define SLF_OUTWAIT	4		/* is outpacket was flag	*/
+
+  unsigned char		mode;		/* SLIP mode			*/
+  unsigned char		leased;
+  pid_t			pid;
+#define SL_MODE_SLIP	0
+#define SL_MODE_CSLIP	1
+#define SL_MODE_SLIP6	2		/* Matt Dillon's printable slip */
+#define SL_MODE_CSLIP6	(SL_MODE_SLIP6|SL_MODE_CSLIP)
+#define SL_MODE_AX25	4
+#define SL_MODE_ADAPTIVE 8
+#ifdef CONFIG_SLIP_SMART
+  unsigned char		outfill;	/* # of sec between outfill packet */
+  unsigned char		keepalive;	/* keepalive seconds		*/
+  struct timer_list	outfill_timer;
+  struct timer_list	keepalive_timer;
+#endif
+};
+
+#define SLIP_MAGIC 0x5302
+
+#endif	/* _LINUX_SLIP.H */