From fa97c3dd10d3b74f4774ea21b2d80fcffa7feb48 Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Sun, 3 Mar 2019 18:56:18 +0100
Subject: devip: simplify ip reassembly functions, getting rid of Ipfrag.hlen

given that we now keep the block size consistent with the
ip packet size, the variable header part of the ip packet
is just: BLEN(bp) - fp->flen == fp->hlen.

fix bug in ip6reassemble() in the non-fragmented case:
reload ih after ip header was moved before writing ih->ploadlen.

use concatbloc() instead of pullupblock().
---
 sys/src/9/ip/ip.c | 41 +++++++++++++++++------------------------
 1 file changed, 17 insertions(+), 24 deletions(-)

(limited to 'sys/src/9/ip/ip.c')

diff --git a/sys/src/9/ip/ip.c b/sys/src/9/ip/ip.c
index a198e7dd7..d648a3217 100644
--- a/sys/src/9/ip/ip.c
+++ b/sys/src/9/ip/ip.c
@@ -408,27 +408,24 @@ ipstats(Fs *f, char *buf, int len)
 static Block*
 ip4reassemble(IP *ip, int offset, Block *bp)
 {
-	int fend;
+	int ovlap, fragsize, len;
+	ulong src, dst;
 	ushort id;
+	Block *bl, **l, *prev;
 	Fragment4 *f, *fnext;
-	Ip4hdr *ih;
-	ulong src, dst;
 	Ipfrag *fp, *fq;
-	Block *bl, **l, *prev;
-	int ovlap, len, fragsize, pktposn;
+	Ip4hdr *ih;
 
 	/*
-	 *  block lists are too hard, pullupblock into a single block
+	 *  block lists are too hard, concatblock into a single block
 	 */
-	if(bp->next != nil)
-		bp = pullupblock(bp, blocklen(bp));
+	bp = concatblock(bp);
 
 	ih = (Ip4hdr*)bp->rp;
 	src = nhgetl(ih->src);
 	dst = nhgetl(ih->dst);
 	id = nhgets(ih->id);
-	len = nhgets(ih->length);
-	fragsize = len - ((ih->vihl&0xF)<<2);
+	fragsize = BLEN(bp) - ((ih->vihl&0xF)<<2);
 
 	qlock(&ip->fraglock4);
 
@@ -467,7 +464,6 @@ ip4reassemble(IP *ip, int offset, Block *bp)
 	fp = (Ipfrag*)bp->base;
 	fp->foff = (offset & 0x1fff)<<3;
 	fp->flen = fragsize;
-	fp->hlen = len - fragsize;
 
 	/* First fragment allocates a reassembly queue */
 	if(f == nil) {
@@ -517,19 +513,19 @@ ip4reassemble(IP *ip, int offset, Block *bp)
 	/* Check to see if succeeding segments overlap */
 	if(bp->next != nil) {
 		l = &bp->next;
-		fend = fp->foff + fp->flen;
+		offset = fp->foff + fp->flen;
 		/* Take completely covered segments out */
 		while((bl = *l) != nil) {
 			fq = (Ipfrag*)bl->base;
-			ovlap = fend - fq->foff;
+			ovlap = offset - fq->foff;
 			if(ovlap <= 0)
 				break;
 			if(ovlap < fq->flen) {
-				fq->flen -= ovlap;
-				fq->foff += ovlap;
 				/* move up ip header */
-				memmove(bl->rp + ovlap, bl->rp, fq->hlen);
+				memmove(bl->rp + ovlap, bl->rp, BLEN(bl) - fq->flen);
 				bl->rp += ovlap;
+				fq->flen -= ovlap;
+				fq->foff += ovlap;
 				break;
 			}
 			*l = bl->next;
@@ -542,10 +538,10 @@ ip4reassemble(IP *ip, int offset, Block *bp)
 	 *  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 != nil; bl = bl->next, pktposn += fp->flen) {
+	offset = 0;
+	for(bl = f->blist; bl != nil; bl = bl->next, offset += fp->flen) {
 		fp = (Ipfrag*)bl->base;
-		if(fp->foff != pktposn)
+		if(fp->foff != offset)
 			break;
 
 		ih = (Ip4hdr*)bl->rp;
@@ -553,9 +549,7 @@ ip4reassemble(IP *ip, int offset, Block *bp)
 			continue;
 
 		bl = f->blist;
-		fq = (Ipfrag*)bl->base;
-		len = fq->hlen + fq->flen;
-		bl->wp = bl->rp + len;
+		len = BLEN(bl);
 
 		/*
 		 * Pullup all the fragment headers and
@@ -564,9 +558,8 @@ ip4reassemble(IP *ip, int offset, Block *bp)
 		for(bl = bl->next; bl != nil && len < IP_MAX; bl = bl->next) {
 			fq = (Ipfrag*)bl->base;
 			fragsize = fq->flen;
+			bl->rp = bl->wp - fragsize;
 			len += fragsize;
-			bl->rp += fq->hlen;
-			bl->wp = bl->rp + fragsize;
 		}
 
 		if(len >= IP_MAX){
-- 
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