ref: 53fbb0515159465421053c3165b1aa9da196aa4d
dir: /sys/src/cmd/ip/ppp/thw.c/
#include <u.h>
#include <libc.h>
#include <ip.h>
#include <auth.h>
#include "ppp.h"
#include "thwack.h"
typedef struct Cstate Cstate;
struct Cstate
{
ulong seq;
Thwack th;
ulong stats[ThwStats];
};
typedef struct Uncstate Uncstate;
struct Uncstate
{
QLock ackl; /* lock for acks sent back to compressor */
int doack; /* send an ack? */
int badpacks; /* bad packets seen in a row */
ulong ackseq; /* packets to ack */
int ackmask;
int active; /* 0 => waiting for resetack */
int resetid; /* id of most recent reset */
Unthwack ut;
};
enum
{
ThwAcked = 1UL << 23,
ThwCompMask = 3UL << 21,
ThwCompressed = 0UL << 21,
ThwUncomp = 1UL << 21,
ThwUncompAdd = 2UL << 21, /* uncompressed, but add to decompression buffer */
ThwSeqMask = 0x0fffff,
ThwSmallPack = 96,
};
static void *compinit(PPP*);
static Block* comp(PPP*, ushort, Block*, int*);
static Block *compresetreq(void*, Block*);
static void compcompack(void*, Block*);
static void compfini(void*);
static void *uncinit(PPP*);
static Block* uncomp(PPP*, Block*, int *protop, Block**);
static void uncfini(void*);
static void uncresetack(void*, Block*);
Comptype cthwack = {
compinit,
comp,
compresetreq,
compfini
};
Uncomptype uncthwack = {
uncinit,
uncomp,
uncresetack,
uncfini
};
static void *
compinit(PPP *)
{
Cstate *cs;
cs = mallocz(sizeof(Cstate), 1);
thwackinit(&cs->th);
return cs;
}
static void
compfini(void *as)
{
Cstate *cs;
cs = as;
thwackcleanup(&cs->th);
free(cs);
}
static Block *
compresetreq(void *as, Block *b)
{
Cstate *cs;
Lcpmsg *m;
int id;
cs = as;
m = (Lcpmsg*)b->rptr;
id = m->id;
thwackinit(&cs->th);
freeb(b);
netlog("thwack resetreq id=%d \n", id);
b = alloclcp(Lresetack, id, 4, &m);
hnputs(m->len, 4);
return b;
}
static Block*
comp(PPP *ppp, ushort proto, Block *b, int *protop)
{
Uncstate *uncs;
Cstate *cs;
Block *bb;
ulong seq, acked;
int n, nn, mustadd;
cs = ppp->cstate;
*protop = 0;
/* put ack and protocol into b */
n = BLEN(b);
if(b->rptr - (2+4) < b->base)
sysfatal("thwack: not enough header in block");
acked = 0;
if(ppp->unctype == &uncthwack){
uncs = ppp->uncstate;
qlock(&uncs->ackl);
if(uncs->doack){
uncs->doack = 0;
b->rptr -= 4;
b->rptr[0] = uncs->ackseq >> 16;
b->rptr[1] = uncs->ackseq >> 8;
b->rptr[2] = uncs->ackseq;
b->rptr[3] = uncs->ackmask;
acked = ThwAcked;
}
qunlock(&uncs->ackl);
}
if(proto > 0xff){
b->rptr -= 2;
b->rptr[0] = proto >> 8;
b->rptr[1] = proto;
}else{
b->rptr--;
b->rptr[0] = proto;
}
bb = allocb(BLEN(b) + 3);
seq = cs->seq;
if(n <= 3){
mustadd = 0;
nn = -1;
}else{
mustadd = n < ThwSmallPack;
nn = thwack(&cs->th, mustadd, bb->wptr + 3, n - 3, b, seq, cs->stats);
}
if(nn < 0 && !mustadd){
if(!acked || BLEN(b) + 1 > ppp->mtu){
freeb(bb);
if(acked)
b->rptr += 4;
if(proto > 0xff)
b->rptr += 2;
else
b->rptr++;
*protop = proto;
return b;
}
bb->wptr[0] = (ThwUncomp | ThwAcked) >> 16;
memmove(bb->wptr + 1, b->rptr, BLEN(b));
bb->wptr += BLEN(b) + 1;
freeb(b);
}else{
cs->seq = (seq + 1) & ThwSeqMask;
if(nn < 0){
nn = BLEN(b);
memmove(bb->wptr + 3, b->rptr, nn);
seq |= ThwUncompAdd;
}else
seq |= ThwCompressed;
seq |= acked;
bb->wptr[0] = seq>>16;
bb->wptr[1] = seq>>8;
bb->wptr[2] = seq;
bb->wptr += nn + 3;
}
*protop = Pcdata;
return bb;
}
static void *
uncinit(PPP *)
{
Uncstate *s;
s = mallocz(sizeof(Uncstate), 1);
s->active = 1;
unthwackinit(&s->ut);
return s;
}
static void
uncfini(void *as)
{
free(as);
}
static void
uncresetack(void *as, Block *b)
{
Uncstate *s;
Lcpmsg *m;
s = as;
m = (Lcpmsg*)b->rptr;
/*
* rfc 1962 says we must reset every message
* we don't since we may have acked some messages
* which the compressor will use in the future.
*/
netlog("unthwack resetack id=%d resetid=%d active=%d\n", m->id, s->resetid, s->active);
if(m->id == (uchar)s->resetid && !s->active){
s->active = 1;
unthwackinit(&s->ut);
}
}
static Block*
uncomp(PPP *ppp, Block *bb, int *protop, Block **reply)
{
Lcpmsg *m;
Cstate *cs;
Uncstate *uncs;
Block *b, *r;
ulong seq, mseq;
ushort proto;
uchar mask;
int n;
*reply = nil;
*protop = 0;
uncs = ppp->uncstate;
if(BLEN(bb) < 4){
syslog(0, "ppp", ": thwack: short packet");
freeb(bb);
return nil;
}
if(!uncs->active){
netlog("unthwack: inactive, killing packet\n");
freeb(bb);
r = alloclcp(Lresetreq, uncs->resetid, 4, &m);
hnputs(m->len, 4);
*reply = r;
return nil;
}
seq = bb->rptr[0] << 16;
if((seq & ThwCompMask) == ThwUncomp){
bb->rptr++;
b = bb;
}else{
seq |= (bb->rptr[1]<<8) | bb->rptr[2];
bb->rptr += 3;
if((seq & ThwCompMask) == ThwCompressed){
b = allocb(ThwMaxBlock);
n = unthwack(&uncs->ut, b->wptr, ThwMaxBlock, bb->rptr, BLEN(bb), seq & ThwSeqMask);
freeb(bb);
if(n < 2){
syslog(0, "ppp", ": unthwack: short or corrupted packet %d seq=%ld", n, seq);
netlog("unthwack: short or corrupted packet n=%d seq=%ld: %s\n", n, seq, uncs->ut.err);
freeb(b);
r = alloclcp(Lresetreq, ++uncs->resetid, 4, &m);
hnputs(m->len, 4);
*reply = r;
uncs->active = 0;
return nil;
}
b->wptr += n;
}else{
unthwackadd(&uncs->ut, bb->rptr, BLEN(bb), seq & ThwSeqMask);
b = bb;
}
/*
* update ack state
*/
mseq = unthwackstate(&uncs->ut, &mask);
qlock(&uncs->ackl);
uncs->ackseq = mseq;
uncs->ackmask = mask;
uncs->doack = 1;
qunlock(&uncs->ackl);
}
/*
* grab the compressed protocol field
*/
proto = *b->rptr++;
if((proto & 1) == 0)
proto = (proto << 8) | *b->rptr++;
*protop = proto;
/*
* decode the ack, and forward to compressor
*/
if(seq & ThwAcked){
if(ppp->ctype == &cthwack){
cs = ppp->cstate;
mseq = (b->rptr[0]<<16) | (b->rptr[1]<<8) | b->rptr[2];
mask = b->rptr[3];
thwackack(&cs->th, mseq, mask);
}
b->rptr += 4;
}
return b;
}