/* Copyright © 1994-1999 Lucent Technologies Inc.  All rights reserved.
 * Portions Copyright © 1997-1999 Vita Nuova Limited
 * Portions Copyright © 2000-2007 Vita Nuova Holdings Limited
 *                                (www.vitanuova.com)
 * Revisions Copyright © 2000-2007 Lucent Technologies Inc. and others
 *
 * Modified for the Akaros operating system:
 * Copyright (c) 2013-2014 The Regents of the University of California
 * Copyright (c) 2013-2016 Google Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include <error.h>
#include <net/ip.h>
#include <kmalloc.h>

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 = (32 * 1024),	/* Maximum Internet packet size */
};

#define IPV6CLASS(hdr) ((hdr->vcf[0]&0x0F)<<2 | (hdr->vcf[1]&0xF0)>>2)
#define BLKIPVER(xp)	(((struct ip6hdr*)((xp)->rp))->vcf[0]&0xF0)
#define NEXT_ID(x) (__sync_add_and_fetch(&(x), 1))
/*
 * This sleazy macro is stolen shamelessly from ip.c, see comment there.
 */
#define BKFG(xp)	((struct Ipfrag*)((xp)->base))
struct fragment6;

struct block *ip6reassemble(struct IP *, int unused_int, struct block *,
                            struct ip6hdr *);
void ipfragfree6(struct IP *, struct fragment6 *);
struct fragment6 *ipfragallo6(struct IP *);
static struct block *procxtns(struct IP *ip, struct block *bp, int doreasm);
int unfraglen(struct block *bp, uint8_t * nexthdr, int setfh);
struct block *procopts(struct block *bp);

/* MIB II counters */
enum {
	Forwarding,
	DefaultTTL,
	InReceives,
	InHdrErrors,
	InAddrErrors,
	ForwDatagrams,
	InUnknownProtos,
	InDiscards,
	InDelivers,
	OutRequests,
	OutDiscards,
	OutNoRoutes,
	ReasmTimeout,
	ReasmReqds,
	ReasmOKs,
	ReasmFails,
	FragOKs,
	FragFails,
	FragCreates,

	Nstats,
};

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",
};

struct Fragment4 {
	struct block *blist;
	struct fragment4 *next;
	uint32_t src;
	uint32_t dst;
	uint16_t id;
	uint64_t age;
};

struct fragment6 {
	struct block *blist;
	struct fragment6 *next;
	uint8_t src[IPaddrlen];
	uint8_t dst[IPaddrlen];
	unsigned int id;
	uint64_t age;
};

struct Ipfrag {
	uint16_t foff;
	uint16_t flen;
};

/* an instance of IP */
struct IP {
	uint32_t stats[Nstats];

	qlock_t fraglock4;
	struct fragment4 *flisthead4;
	struct fragment4 *fragfree4;
	int id4;

	qlock_t fraglock6;
	struct fragment6 *flisthead6;
	struct fragment6 *fragfree6;
	int id6;

	int iprouting;		/* true if we route like a gateway */
};

int ipoput6(struct Fs *f, struct block *bp,
            int gating, int ttl, int tos, struct conv *c)
{
	ERRSTACK(1);
	int tentative;
	struct Ipifc *ifc;
	uint8_t *gate, nexthdr;
	struct ip6hdr *eh;
	int medialen, len, chunk, uflen, flen, seglen, lid, offset, fragoff;
	int morefrags, blklen;
	struct route *r, *sr;
	struct fraghdr6 fraghdr;
	struct block *xp, *nb;
	struct IP *ip;
	int rv = 0;

	ip = f->ip;

	/* Sanity check for our transport protocols. */
	if (bp->mss)
		assert(bp->flag & Btso);
	/* Fill out the ip header */
	eh = (struct ip6hdr *)(bp->rp);

	ip->stats[OutRequests]++;

	/* Number of uint8_ts in data and ip header to write */
	len = blocklen(bp);

	tentative = iptentative(f, eh->src);
	if (tentative) {
		netlog(f, Logip,
		       "reject tx of packet with tentative src address\n");
		goto free;
	}

	if (gating) {
		chunk = nhgets(eh->ploadlen);
		if (chunk > len) {
			ip->stats[OutDiscards]++;
			netlog(f, Logip, "short gated packet\n");
			goto free;
		}
		if (chunk + IPV6HDR_LEN < len)
			len = chunk + IPV6HDR_LEN;
	}

	if (len >= IP_MAX) {
		ip->stats[OutDiscards]++;
		netlog(f, Logip, "exceeded ip max size %I\n", eh->dst);
		goto free;
	}

	r = v6lookup(f, eh->dst, c);
	if (r == NULL) {
		ip->stats[OutNoRoutes]++;
		netlog(f, Logip, "no interface %I\n", eh->dst);
		rv = -1;
		goto free;
	}

	ifc = r->rt.ifc;
	if (r->rt.type & (Rifc | Runi))
		gate = eh->dst;
	else if (r->rt.type & (Rbcast | Rmulti)) {
		gate = eh->dst;
		sr = v6lookup(f, eh->src, NULL);
		if (sr != NULL && (sr->rt.type & Runi))
			ifc = sr->rt.ifc;
	} else
		gate = r->v6.gate;

	if (!gating)
		eh->vcf[0] = IP_VER6;
	eh->ttl = ttl;
	if (!gating) {
		eh->vcf[0] |= (tos >> 4);
		eh->vcf[1] = (tos << 4);
	}

	if (!canrlock(&ifc->rwlock)) {
		goto free;
	}

	if (waserror()) {
		runlock(&ifc->rwlock);
		nexterror();
	}

	if (ifc->m == NULL) {
		goto raise;
	}

	/* If we dont need to fragment just send it */
	medialen = ifc->maxtu - ifc->m->hsize;
	if (len <= medialen) {
		hnputs(eh->ploadlen, len - IPV6HDR_LEN);
		ifc->m->bwrite(ifc, bp, V6, gate);
		runlock(&ifc->rwlock);
		poperror();
		return 0;
	}

	if (gating)
		if (ifc->reassemble <= 0) {
			/*
			 * v6 intermediate nodes are not supposed to fragment
			 * pkts; we fragment if ifc->reassemble is turned on; an
			 * exception needed for nat.
			 */
			ip->stats[OutDiscards]++;
			icmppkttoobig6(f, ifc, bp);
			netlog(f, Logip, "%I: gated pkts not fragmented\n",
			       eh->dst);
			goto raise;
		}

	/* start v6 fragmentation */
	uflen = unfraglen(bp, &nexthdr, 1);
	if (uflen > medialen) {
		ip->stats[FragFails]++;
		ip->stats[OutDiscards]++;
		netlog(f, Logip, "%I: unfragmentable part too big\n", eh->dst);
		goto raise;
	}

	flen = len - uflen;
	seglen = (medialen - (uflen + IP6FHDR)) & ~7;
	if (seglen < 8) {
		ip->stats[FragFails]++;
		ip->stats[OutDiscards]++;
		netlog(f, Logip, "%I: seglen < 8\n", eh->dst);
		goto raise;
	}

	lid = NEXT_ID(ip->id6);
	fraghdr.nexthdr = nexthdr;
	fraghdr.res = 0;
	hnputl(fraghdr.id, lid);

	xp = bp;
	offset = uflen;
	while (xp != NULL && offset && offset >= BLEN(xp)) {
		offset -= BLEN(xp);
		xp = xp->next;
	}
	xp->rp += offset;

	fragoff = 0;
	morefrags = 1;

	for (; fragoff < flen; fragoff += seglen) {
		nb = block_alloc(uflen + IP6FHDR + seglen, MEM_WAIT);

		if (fragoff + seglen >= flen) {
			seglen = flen - fragoff;
			morefrags = 0;
		}

		hnputs(eh->ploadlen, seglen + IP6FHDR);
		memmove(nb->wp, eh, uflen);
		nb->wp += uflen;

		hnputs(fraghdr.offsetRM, fragoff);	// last 3 bits must be 0
		fraghdr.offsetRM[1] |= morefrags;
		memmove(nb->wp, &fraghdr, IP6FHDR);
		nb->wp += IP6FHDR;

		/* Copy data */
		chunk = seglen;
		while (chunk) {
			if (!xp) {
				ip->stats[OutDiscards]++;
				ip->stats[FragFails]++;
				freeblist(nb);
				netlog(f, Logip, "!xp: chunk in v6%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;
		}

		ifc->m->bwrite(ifc, nb, V6, gate);
		ip->stats[FragCreates]++;
	}
	ip->stats[FragOKs]++;

raise:
	runlock(&ifc->rwlock);
	poperror();
free:
	freeblist(bp);
	return rv;
}

void ipiput6(struct Fs *f, struct Ipifc *ifc, struct block *bp)
{
	int hl;
	int hop, tos;
	uint8_t proto;
	struct ip6hdr *h;
	struct Proto *p;
	int notforme;
	int tentative;
	uint8_t v6dst[IPaddrlen];
	struct IP *ip;
	struct route *r, *sr;

	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 < IP6HDR)
			hl = IP6HDR;
		if (hl > 64)
			hl = 64;
		bp = pullupblock(bp, hl);
		if (bp == NULL)
			return;
	}

	h = (struct ip6hdr *)(bp->rp);

	memmove(&v6dst[0], &(h->dst)[0], IPaddrlen);
	notforme = ipforme(f, v6dst) == 0;
	tentative = iptentative(f, v6dst);

	if (tentative && (h->proto != ICMPv6)) {
		printd("tentative addr, drop\n");
		freeblist(bp);
		return;
	}

	/* Check header version */
	if (BLKIPVER(bp) != IP_VER6) {
		ip->stats[InHdrErrors]++;
		netlog(f, Logip, "ip: bad version 0x%x\n",
		       (h->vcf[0] & 0xF0) >> 2);
		freeblist(bp);
		return;
	}

	/* route */
	if (notforme) {
		if (!ip->iprouting) {
			freeb(bp);
			return;
		}
		/* don't forward to source's network */
		sr = v6lookup(f, h->src, NULL);
		r = v6lookup(f, h->dst, NULL);

		if (r == NULL || sr == r) {
			ip->stats[OutDiscards]++;
			freeblist(bp);
			return;
		}

		/* don't forward if packet has timed out */
		hop = h->ttl;
		if (hop < 1) {
			ip->stats[InHdrErrors]++;
			icmpttlexceeded6(f, ifc, bp);
			freeblist(bp);
			return;
		}

		/* process headers & reassemble if the interface expects it */
		bp = procxtns(ip, bp, r->rt.ifc->reassemble);

		if (bp == NULL)
			return;

		ip->stats[ForwDatagrams]++;
		h = (struct ip6hdr *)(bp->rp);
		tos = IPV6CLASS(h);
		hop = h->ttl;
		ipoput6(f, bp, 1, hop - 1, tos, NULL);
		return;
	}

	/* reassemble & process headers if needed */
	bp = procxtns(ip, bp, 1);

	if (bp == NULL)
		return;

	h = (struct ip6hdr *)(bp->rp);
	proto = h->proto;
	p = Fsrcvpcol(f, proto);
	if (p != NULL && p->rcv != NULL) {
		ip->stats[InDelivers]++;
		(*p->rcv) (p, ifc, bp);
		return;
	}

	ip->stats[InDiscards]++;
	ip->stats[InUnknownProtos]++;
	freeblist(bp);
}

/*
 * ipfragfree6 - copied from ipfragfree4 - assume hold fraglock6
 */
void ipfragfree6(struct IP *ip, struct fragment6 *frag)
{
	struct fragment6 *fl, **l;

	if (frag->blist)
		freeblist(frag->blist);

	memset(frag->src, 0, IPaddrlen);
	frag->id = 0;
	frag->blist = NULL;

	l = &ip->flisthead6;
	for (fl = *l; fl; fl = fl->next) {
		if (fl == frag) {
			*l = frag->next;
			break;
		}
		l = &fl->next;
	}

	frag->next = ip->fragfree6;
	ip->fragfree6 = frag;

}

/*
 * ipfragallo6 - copied from ipfragalloc4
 */
struct fragment6 *ipfragallo6(struct IP *ip)
{
	struct fragment6 *f;

	while (ip->fragfree6 == NULL) {
		/* free last entry on fraglist */
		for (f = ip->flisthead6; f->next; f = f->next) ;
		ipfragfree6(ip, f);
	}
	f = ip->fragfree6;
	ip->fragfree6 = f->next;
	f->next = ip->flisthead6;
	ip->flisthead6 = f;
	f->age = NOW + 30000;

	return f;
}

static struct block *procxtns(struct IP *ip, struct block *bp, int doreasm)
{

	int offset;
	uint8_t proto;
	struct ip6hdr *h;

	h = (struct ip6hdr *)(bp->rp);
	offset = unfraglen(bp, &proto, 0);

	if ((proto == FH) && (doreasm != 0)) {
		bp = ip6reassemble(ip, offset, bp, h);
		if (bp == NULL)
			return NULL;
		offset = unfraglen(bp, &proto, 0);
	}

	if (proto == DOH || offset > IP6HDR)
		bp = procopts(bp);

	return bp;
}

/* returns length of "Unfragmentable part", i.e., sum of lengths of ipv6 hdr,
 * hop-by-hop & routing headers if present; *nexthdr is set to nexthdr value of
 * the last header in the "Unfragmentable part"; if setfh != 0, nexthdr field of
 * the last header in the "Unfragmentable part" is set to FH.
 */
int unfraglen(struct block *bp, uint8_t * nexthdr, int setfh)
{
	uint8_t *p, *q;
	int ufl, hs;

	p = bp->rp;
	q = p + 6; /* proto, = p+sizeof(Ip6hdr.vcf)+sizeof(Ip6hdr.ploadlen) */
	*nexthdr = *q;
	ufl = IP6HDR;
	p += ufl;

	for (;;) {
		if (*nexthdr == HBH || *nexthdr == RH) {
			*nexthdr = *p;
			hs = ((int)*(p + 1) + 1) * 8;
			ufl += hs;
			q = p;
			p += hs;
		} else
			break;
	}

	if (*nexthdr == FH)
		*q = *p;

	if (setfh)
		*q = FH;

	return ufl;
}

struct block *procopts(struct block *bp)
{
	return bp;
}

struct block *ip6reassemble(struct IP *ip, int uflen, struct block *bp,
                            struct ip6hdr *ih)
{

	int fend, offset;
	unsigned int id;
	struct fragment6 *f, *fnext;
	struct fraghdr6 *fraghdr;
	uint8_t src[IPaddrlen], dst[IPaddrlen];
	struct block *bl, **l, *last, *prev;
	int ovlap, len, fragsize, pktposn;

	fraghdr = (struct fraghdr6 *)(bp->rp + uflen);
	memmove(src, ih->src, IPaddrlen);
	memmove(dst, ih->dst, IPaddrlen);
	id = nhgetl(fraghdr->id);
	offset = nhgets(fraghdr->offsetRM) & ~7;

	/*
	 *  block lists are too hard, pullupblock into a single block
	 */
	if (bp->next) {
		bp = pullupblock(bp, blocklen(bp));
		ih = (struct ip6hdr *)(bp->rp);
	}

	qlock(&ip->fraglock6);

	/*
	 *  find a reassembly queue for this fragment
	 */
	for (f = ip->flisthead6; f; f = fnext) {
		fnext = f->next;
		if (ipcmp(f->src, src) == 0 && ipcmp(f->dst, dst) == 0
		    && f->id == id)
			break;
		if (f->age < NOW) {
			ip->stats[ReasmTimeout]++;
			ipfragfree6(ip, f);
		}
	}

	/*
	 *  if this isn't a fragmented packet, accept it
	 *  and get rid of any fragments that might go
	 *  with it.
	 */
	if (nhgets(fraghdr->offsetRM) == 0) {	// first frag is also the last
		if (f != NULL) {
			ipfragfree6(ip, f);
			ip->stats[ReasmFails]++;
		}
		qunlock(&ip->fraglock6);
		return bp;
	}

	if (bp->base + sizeof(struct Ipfrag) >= bp->rp) {
		bp = padblock(bp, sizeof(struct Ipfrag));
		bp->rp += sizeof(struct Ipfrag);
	}

	BKFG(bp)->foff = offset;
	BKFG(bp)->flen = nhgets(ih->ploadlen) + IP6HDR - uflen - IP6FHDR;

	/* First fragment allocates a reassembly queue */
	if (f == NULL) {
		f = ipfragallo6(ip);
		f->id = id;
		memmove(f->src, src, IPaddrlen);
		memmove(f->dst, dst, IPaddrlen);

		f->blist = bp;

		qunlock(&ip->fraglock6);
		ip->stats[ReasmReqds]++;
		return NULL;
	}

	/*
	 *  find the new fragment's position in the queue
	 */
	prev = NULL;
	l = &f->blist;
	bl = f->blist;
	while (bl != NULL && 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->fraglock6);
				return NULL;
			}
			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, uflen);
				(*l)->rp += ovlap;
				break;
			}
			last = (*l)->next;
			(*l)->next = NULL;
			freeblist(*l);
			*l = last;
		}
	}

	/*
	 *  look for a complete packet.  if we get to a fragment
	 *  with the trailing bit of fraghdr->offsetRM[1] set, we're done.
	 */
	pktposn = 0;
	for (bl = f->blist; bl; bl = bl->next) {
		if (BKFG(bl)->foff != pktposn)
			break;

		fraghdr = (struct fraghdr6 *)(bl->rp + uflen);
		if ((fraghdr->offsetRM[1] & 1) == 0) {
			bl = f->blist;

			/* get rid of frag header in first fragment */

			memmove(bl->rp + IP6FHDR, bl->rp, uflen);
			bl->rp += IP6FHDR;
			len = nhgets(((struct ip6hdr *)(bl->rp))->ploadlen) -
				IP6FHDR;
			bl->wp = bl->rp + len + IP6HDR;

			/* 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 += uflen + IP6FHDR;
				bl->wp = bl->rp + fragsize;
			}

			bl = f->blist;
			f->blist = NULL;
			ipfragfree6(ip, f);
			ih = (struct ip6hdr *)(bl->rp);
			hnputs(ih->ploadlen, len);
			qunlock(&ip->fraglock6);
			ip->stats[ReasmOKs]++;
			return bl;
		}
		pktposn += BKFG(bl)->flen;
	}
	qunlock(&ip->fraglock6);

	return NULL;
}