ref: c116550e6a41572796e4db65e4f6acbcb3d9d6f8
dir: /os/ip/ip.c/
#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"
#include "ip.h"
typedef struct Ip4hdr Ip4hdr;
typedef struct IP IP;
typedef struct Fragment4 Fragment4;
typedef struct Fragment6 Fragment6;
typedef struct Ipfrag Ipfrag;
enum
{
IP4HDR = 20, /* sizeof(Ip4hdr) */
IP6HDR = 40, /* sizeof(Ip6hdr) */
IP_HLEN4 = 0x05, /* Header length in words */
IP_DF = 0x4000, /* Don't fragment */
IP_MF = 0x2000, /* More fragments */
IP6FHDR = 8, /* sizeof(Fraghdr6) */
IP_MAX = 64*1024, /* Maximum Internet packet size */
};
#define BLKIPVER(xp) (((Ip4hdr*)((xp)->rp))->vihl&0xF0)
struct Ip4hdr
{
uchar vihl; /* Version and header length */
uchar tos; /* Type of service */
uchar length[2]; /* packet length */
uchar id[2]; /* ip->identification */
uchar frag[2]; /* Fragment information */
uchar ttl; /* Time to live */
uchar proto; /* Protocol */
uchar cksum[2]; /* Header checksum */
uchar src[4]; /* IP source */
uchar dst[4]; /* IP destination */
};
/* MIB II counters */
enum
{
Forwarding,
DefaultTTL,
InReceives,
InHdrErrors,
InAddrErrors,
ForwDatagrams,
InUnknownProtos,
InDiscards,
InDelivers,
OutRequests,
OutDiscards,
OutNoRoutes,
ReasmTimeout,
ReasmReqds,
ReasmOKs,
ReasmFails,
FragOKs,
FragFails,
FragCreates,
Nstats,
};
struct Fragment4
{
Block* blist;
Fragment4* next;
ulong src;
ulong dst;
ushort id;
ulong age;
};
struct Fragment6
{
Block* blist;
Fragment6* next;
uchar src[IPaddrlen];
uchar dst[IPaddrlen];
uint id;
ulong age;
};
struct Ipfrag
{
ushort foff;
ushort flen;
};
/* an instance of IP */
struct IP
{
ulong stats[Nstats];
QLock fraglock4;
Fragment4* flisthead4;
Fragment4* fragfree4;
Ref id4;
QLock fraglock6;
Fragment6* flisthead6;
Fragment6* fragfree6;
Ref id6;
int iprouting; /* true if we route like a gateway */
};
static char *statnames[] =
{
[Forwarding] "Forwarding",
[DefaultTTL] "DefaultTTL",
[InReceives] "InReceives",
[InHdrErrors] "InHdrErrors",
[InAddrErrors] "InAddrErrors",
[ForwDatagrams] "ForwDatagrams",
[InUnknownProtos] "InUnknownProtos",
[InDiscards] "InDiscards",
[InDelivers] "InDelivers",
[OutRequests] "OutRequests",
[OutDiscards] "OutDiscards",
[OutNoRoutes] "OutNoRoutes",
[ReasmTimeout] "ReasmTimeout",
[ReasmReqds] "ReasmReqds",
[ReasmOKs] "ReasmOKs",
[ReasmFails] "ReasmFails",
[FragOKs] "FragOKs",
[FragFails] "FragFails",
[FragCreates] "FragCreates",
};
#define BLKIP(xp) ((Ip4hdr*)((xp)->rp))
/*
* This sleazy macro relies on the media header size being
* larger than sizeof(Ipfrag). ipreassemble checks this is true
*/
#define BKFG(xp) ((Ipfrag*)((xp)->base))
ushort ipcsum(uchar*);
Block* ip4reassemble(IP*, int, Block*, Ip4hdr*);
void ipfragfree4(IP*, Fragment4*);
Fragment4* ipfragallo4(IP*);
void
ip_init_6(Fs *f)
{
V6params *v6p;
v6p = smalloc(sizeof(V6params));
v6p->rp.mflag = 0; // default not managed
v6p->rp.oflag = 0;
v6p->rp.maxraint = 600000; // millisecs
v6p->rp.minraint = 200000;
v6p->rp.linkmtu = 0; // no mtu sent
v6p->rp.reachtime = 0;
v6p->rp.rxmitra = 0;
v6p->rp.ttl = MAXTTL;
v6p->rp.routerlt = 3*(v6p->rp.maxraint);
v6p->hp.rxmithost = 1000; // v6 RETRANS_TIMER
v6p->cdrouter = -1;
f->v6p = v6p;
}
void
initfrag(IP *ip, int size)
{
Fragment4 *fq4, *eq4;
Fragment6 *fq6, *eq6;
ip->fragfree4 = (Fragment4*)malloc(sizeof(Fragment4) * size);
if(ip->fragfree4 == nil)
panic("initfrag");
eq4 = &ip->fragfree4[size];
for(fq4 = ip->fragfree4; fq4 < eq4; fq4++)
fq4->next = fq4+1;
ip->fragfree4[size-1].next = nil;
ip->fragfree6 = (Fragment6*)malloc(sizeof(Fragment6) * size);
if(ip->fragfree6 == nil)
panic("initfrag");
eq6 = &ip->fragfree6[size];
for(fq6 = ip->fragfree6; fq6 < eq6; fq6++)
fq6->next = fq6+1;
ip->fragfree6[size-1].next = nil;
}
void
ip_init(Fs *f)
{
IP *ip;
ip = smalloc(sizeof(IP));
initfrag(ip, 100);
f->ip = ip;
ip_init_6(f);
}
void
iprouting(Fs *f, int on)
{
f->ip->iprouting = on;
if(f->ip->iprouting==0)
f->ip->stats[Forwarding] = 2;
else
f->ip->stats[Forwarding] = 1;
}
int
ipoput4(Fs *f, Block *bp, int gating, int ttl, int tos, Conv *c)
{
Ipifc *ifc;
uchar *gate;
ulong fragoff;
Block *xp, *nb;
Ip4hdr *eh, *feh;
int lid, len, seglen, chunk, dlen, blklen, offset, medialen;
Route *r, *sr;
IP *ip;
int rv = 0;
ip = f->ip;
/* Fill out the ip header */
eh = (Ip4hdr*)(bp->rp);
ip->stats[OutRequests]++;
/* Number of uchars in data and ip header to write */
len = blocklen(bp);
if(gating){
chunk = nhgets(eh->length);
if(chunk > len){
ip->stats[OutDiscards]++;
netlog(f, Logip, "short gated packet\n");
goto free;
}
if(chunk < len)
len = chunk;
}
if(len >= IP_MAX){
ip->stats[OutDiscards]++;
netlog(f, Logip, "exceeded ip max size %V\n", eh->dst);
goto free;
}
r = v4lookup(f, eh->dst, c);
if(r == nil){
ip->stats[OutNoRoutes]++;
netlog(f, Logip, "no interface %V\n", eh->dst);
rv = -1;
goto free;
}
ifc = r->ifc;
if(r->type & (Rifc|Runi))
gate = eh->dst;
else
if(r->type & (Rbcast|Rmulti)) {
gate = eh->dst;
sr = v4lookup(f, eh->src, nil);
if(sr != nil && (sr->type & Runi))
ifc = sr->ifc;
}
else
gate = r->v4.gate;
if(!gating)
eh->vihl = IP_VER4|IP_HLEN4;
eh->ttl = ttl;
if(!gating)
eh->tos = tos;
if(!canrlock(ifc))
goto free;
if(waserror()){
runlock(ifc);
nexterror();
}
if(ifc->m == nil)
goto raise;
/* If we dont need to fragment just send it */
medialen = ifc->maxtu - ifc->m->hsize;
if(len <= medialen) {
if(!gating)
hnputs(eh->id, incref(&ip->id4));
hnputs(eh->length, len);
if(!gating){
eh->frag[0] = 0;
eh->frag[1] = 0;
}
eh->cksum[0] = 0;
eh->cksum[1] = 0;
hnputs(eh->cksum, ipcsum(&eh->vihl));
ifc->m->bwrite(ifc, bp, V4, gate);
runlock(ifc);
poperror();
return 0;
}
if((eh->frag[0] & (IP_DF>>8)) && !gating) print("%V: DF set\n", eh->dst);
if(eh->frag[0] & (IP_DF>>8)){
ip->stats[FragFails]++;
ip->stats[OutDiscards]++;
icmpcantfrag(f, bp, medialen);
netlog(f, Logip, "%V: eh->frag[0] & (IP_DF>>8)\n", eh->dst);
goto raise;
}
seglen = (medialen - IP4HDR) & ~7;
if(seglen < 8){
ip->stats[FragFails]++;
ip->stats[OutDiscards]++;
netlog(f, Logip, "%V seglen < 8\n", eh->dst);
goto raise;
}
dlen = len - IP4HDR;
xp = bp;
if(gating)
lid = nhgets(eh->id);
else
lid = incref(&ip->id4);
offset = IP4HDR;
while(xp != nil && offset && offset >= BLEN(xp)) {
offset -= BLEN(xp);
xp = xp->next;
}
xp->rp += offset;
if(gating)
fragoff = nhgets(eh->frag)<<3;
else
fragoff = 0;
dlen += fragoff;
for(; fragoff < dlen; fragoff += seglen) {
nb = allocb(IP4HDR+seglen);
feh = (Ip4hdr*)(nb->rp);
memmove(nb->wp, eh, IP4HDR);
nb->wp += IP4HDR;
if((fragoff + seglen) >= dlen) {
seglen = dlen - fragoff;
hnputs(feh->frag, fragoff>>3);
}
else
hnputs(feh->frag, (fragoff>>3)|IP_MF);
hnputs(feh->length, seglen + IP4HDR);
hnputs(feh->id, lid);
/* Copy up the data area */
chunk = seglen;
while(chunk) {
if(!xp) {
ip->stats[OutDiscards]++;
ip->stats[FragFails]++;
freeblist(nb);
netlog(f, Logip, "!xp: chunk %d\n", chunk);
goto raise;
}
blklen = chunk;
if(BLEN(xp) < chunk)
blklen = BLEN(xp);
memmove(nb->wp, xp->rp, blklen);
nb->wp += blklen;
xp->rp += blklen;
chunk -= blklen;
if(xp->rp == xp->wp)
xp = xp->next;
}
feh->cksum[0] = 0;
feh->cksum[1] = 0;
hnputs(feh->cksum, ipcsum(&feh->vihl));
ifc->m->bwrite(ifc, nb, V4, gate);
ip->stats[FragCreates]++;
}
ip->stats[FragOKs]++;
raise:
runlock(ifc);
poperror();
free:
freeblist(bp);
return rv;
}
void
ipiput4(Fs *f, Ipifc *ifc, Block *bp)
{
int hl;
int hop, tos, proto, olen;
Ip4hdr *h;
Proto *p;
ushort frag;
int notforme;
uchar *dp, v6dst[IPaddrlen];
IP *ip;
Route *r;
if(BLKIPVER(bp) != IP_VER4) {
ipiput6(f, ifc, bp);
return;
}
ip = f->ip;
ip->stats[InReceives]++;
/*
* Ensure we have all the header info in the first
* block. Make life easier for other protocols by
* collecting up to the first 64 bytes in the first block.
*/
if(BLEN(bp) < 64) {
hl = blocklen(bp);
if(hl < IP4HDR)
hl = IP4HDR;
if(hl > 64)
hl = 64;
bp = pullupblock(bp, hl);
if(bp == nil)
return;
}
h = (Ip4hdr*)(bp->rp);
/* dump anything that whose header doesn't checksum */
if((bp->flag & Bipck) == 0 && ipcsum(&h->vihl)) {
ip->stats[InHdrErrors]++;
netlog(f, Logip, "ip: checksum error %V\n", h->src);
freeblist(bp);
return;
}
v4tov6(v6dst, h->dst);
notforme = ipforme(f, v6dst) == 0;
/* Check header length and version */
if((h->vihl&0x0F) != IP_HLEN4) {
hl = (h->vihl&0xF)<<2;
if(hl < (IP_HLEN4<<2)) {
ip->stats[InHdrErrors]++;
netlog(f, Logip, "ip: %V bad hivl %ux\n", h->src, h->vihl);
freeblist(bp);
return;
}
/* If this is not routed strip off the options */
if(notforme == 0) {
olen = nhgets(h->length);
dp = bp->rp + (hl - (IP_HLEN4<<2));
memmove(dp, h, IP_HLEN4<<2);
bp->rp = dp;
h = (Ip4hdr*)(bp->rp);
h->vihl = (IP_VER4|IP_HLEN4);
hnputs(h->length, olen-hl+(IP_HLEN4<<2));
}
}
/* route */
if(notforme) {
Conv conv;
if(!ip->iprouting){
freeb(bp);
return;
}
/* don't forward to source's network */
conv.r = nil;
r = v4lookup(f, h->dst, &conv);
if(r == nil || r->ifc == ifc){
ip->stats[OutDiscards]++;
freeblist(bp);
return;
}
/* don't forward if packet has timed out */
hop = h->ttl;
if(hop < 1) {
ip->stats[InHdrErrors]++;
icmpttlexceeded(f, ifc->lifc->local, bp);
freeblist(bp);
return;
}
/* reassemble if the interface expects it */
if(r->ifc == nil) panic("nil route rfc");
if(r->ifc->reassemble){
frag = nhgets(h->frag);
if(frag) {
h->tos = 0;
if(frag & IP_MF)
h->tos = 1;
bp = ip4reassemble(ip, frag, bp, h);
if(bp == nil)
return;
h = (Ip4hdr*)(bp->rp);
}
}
ip->stats[ForwDatagrams]++;
tos = h->tos;
hop = h->ttl;
ipoput4(f, bp, 1, hop - 1, tos, &conv);
return;
}
frag = nhgets(h->frag);
if(frag) {
h->tos = 0;
if(frag & IP_MF)
h->tos = 1;
bp = ip4reassemble(ip, frag, bp, h);
if(bp == nil)
return;
h = (Ip4hdr*)(bp->rp);
}
/* don't let any frag info go up the stack */
h->frag[0] = 0;
h->frag[1] = 0;
proto = h->proto;
p = Fsrcvpcol(f, proto);
if(p != nil && p->rcv != nil) {
ip->stats[InDelivers]++;
(*p->rcv)(p, ifc, bp);
return;
}
ip->stats[InDiscards]++;
ip->stats[InUnknownProtos]++;
freeblist(bp);
}
int
ipstats(Fs *f, char *buf, int len)
{
IP *ip;
char *p, *e;
int i;
ip = f->ip;
ip->stats[DefaultTTL] = MAXTTL;
p = buf;
e = p+len;
for(i = 0; i < Nstats; i++)
p = seprint(p, e, "%s: %lud\n", statnames[i], ip->stats[i]);
return p - buf;
}
Block*
ip4reassemble(IP *ip, int offset, Block *bp, Ip4hdr *ih)
{
int fend;
ushort id;
Fragment4 *f, *fnext;
ulong src, dst;
Block *bl, **l, *last, *prev;
int ovlap, len, fragsize, pktposn;
src = nhgetl(ih->src);
dst = nhgetl(ih->dst);
id = nhgets(ih->id);
/*
* block lists are too hard, pullupblock into a single block
*/
if(bp->next){
bp = pullupblock(bp, blocklen(bp));
ih = (Ip4hdr*)(bp->rp);
}
qlock(&ip->fraglock4);
/*
* find a reassembly queue for this fragment
*/
for(f = ip->flisthead4; f; f = fnext){
fnext = f->next; /* because ipfragfree4 changes the list */
if(f->src == src && f->dst == dst && f->id == id)
break;
if(f->age < NOW){
ip->stats[ReasmTimeout]++;
ipfragfree4(ip, f);
}
}
/*
* if this isn't a fragmented packet, accept it
* and get rid of any fragments that might go
* with it.
*/
if(!ih->tos && (offset & ~(IP_MF|IP_DF)) == 0) {
if(f != nil) {
ipfragfree4(ip, f);
ip->stats[ReasmFails]++;
}
qunlock(&ip->fraglock4);
return bp;
}
if(bp->base+sizeof(Ipfrag) >= bp->rp){
bp = padblock(bp, sizeof(Ipfrag));
bp->rp += sizeof(Ipfrag);
}
BKFG(bp)->foff = offset<<3;
BKFG(bp)->flen = nhgets(ih->length)-IP4HDR;
/* First fragment allocates a reassembly queue */
if(f == nil) {
f = ipfragallo4(ip);
f->id = id;
f->src = src;
f->dst = dst;
f->blist = bp;
qunlock(&ip->fraglock4);
ip->stats[ReasmReqds]++;
return nil;
}
/*
* find the new fragment's position in the queue
*/
prev = nil;
l = &f->blist;
bl = f->blist;
while(bl != nil && BKFG(bp)->foff > BKFG(bl)->foff) {
prev = bl;
l = &bl->next;
bl = bl->next;
}
/* Check overlap of a previous fragment - trim away as necessary */
if(prev) {
ovlap = BKFG(prev)->foff + BKFG(prev)->flen - BKFG(bp)->foff;
if(ovlap > 0) {
if(ovlap >= BKFG(bp)->flen) {
freeblist(bp);
qunlock(&ip->fraglock4);
return nil;
}
BKFG(prev)->flen -= ovlap;
}
}
/* Link onto assembly queue */
bp->next = *l;
*l = bp;
/* Check to see if succeeding segments overlap */
if(bp->next) {
l = &bp->next;
fend = BKFG(bp)->foff + BKFG(bp)->flen;
/* Take completely covered segments out */
while(*l) {
ovlap = fend - BKFG(*l)->foff;
if(ovlap <= 0)
break;
if(ovlap < BKFG(*l)->flen) {
BKFG(*l)->flen -= ovlap;
BKFG(*l)->foff += ovlap;
/* move up ih hdrs */
memmove((*l)->rp + ovlap, (*l)->rp, IP4HDR);
(*l)->rp += ovlap;
break;
}
last = (*l)->next;
(*l)->next = nil;
freeblist(*l);
*l = last;
}
}
/*
* look for a complete packet. if we get to a fragment
* without IP_MF set, we're done.
*/
pktposn = 0;
for(bl = f->blist; bl; bl = bl->next) {
if(BKFG(bl)->foff != pktposn)
break;
if((BLKIP(bl)->frag[0]&(IP_MF>>8)) == 0) {
bl = f->blist;
len = nhgets(BLKIP(bl)->length);
bl->wp = bl->rp + len;
/* Pullup all the fragment headers and
* return a complete packet
*/
for(bl = bl->next; bl; bl = bl->next) {
fragsize = BKFG(bl)->flen;
len += fragsize;
bl->rp += IP4HDR;
bl->wp = bl->rp + fragsize;
}
bl = f->blist;
f->blist = nil;
ipfragfree4(ip, f);
ih = BLKIP(bl);
hnputs(ih->length, len);
qunlock(&ip->fraglock4);
ip->stats[ReasmOKs]++;
return bl;
}
pktposn += BKFG(bl)->flen;
}
qunlock(&ip->fraglock4);
return nil;
}
/*
* ipfragfree4 - Free a list of fragments - assume hold fraglock4
*/
void
ipfragfree4(IP *ip, Fragment4 *frag)
{
Fragment4 *fl, **l;
if(frag->blist)
freeblist(frag->blist);
frag->src = 0;
frag->id = 0;
frag->blist = nil;
l = &ip->flisthead4;
for(fl = *l; fl; fl = fl->next) {
if(fl == frag) {
*l = frag->next;
break;
}
l = &fl->next;
}
frag->next = ip->fragfree4;
ip->fragfree4 = frag;
}
/*
* ipfragallo4 - allocate a reassembly queue - assume hold fraglock4
*/
Fragment4 *
ipfragallo4(IP *ip)
{
Fragment4 *f;
while(ip->fragfree4 == nil) {
/* free last entry on fraglist */
for(f = ip->flisthead4; f->next; f = f->next)
;
ipfragfree4(ip, f);
}
f = ip->fragfree4;
ip->fragfree4 = f->next;
f->next = ip->flisthead4;
ip->flisthead4 = f;
f->age = NOW + 30000;
return f;
}
ushort
ipcsum(uchar *addr)
{
int len;
ulong sum;
sum = 0;
len = (addr[0]&0xf)<<2;
while(len > 0) {
sum += addr[0]<<8 | addr[1] ;
len -= 2;
addr += 2;
}
sum = (sum & 0xffff) + (sum >> 16);
sum = (sum & 0xffff) + (sum >> 16);
return (sum^0xffff);
}