/* * 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/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/system.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; break; 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; } /* 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); #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"); return; } struct slcompress * slhc_init(int rslots, int tslots) { printk(KERN_DEBUG "Called IP function on non IP-system: slhc_init"); return NULL; } EXPORT_SYMBOL(slhc_init); EXPORT_SYMBOL(slhc_free); EXPORT_SYMBOL(slhc_remember); EXPORT_SYMBOL(slhc_compress); EXPORT_SYMBOL(slhc_uncompress); EXPORT_SYMBOL(slhc_toss); #endif /* CONFIG_INET */ MODULE_LICENSE("Dual BSD/GPL");