From 33b446b8bbfea80552d462296d27ad4114fbd3fb Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@swtch.com>
Date: Mon, 25 May 2009 00:30:17 -0700
Subject: libventi: protocol support for blocks larger than 64k

---
 include/venti.h        |  2 +-
 man/man7/venti.7       | 15 +++++++++++++++
 src/libventi/client.c  |  4 ++++
 src/libventi/fcall.c   | 33 +++++++++++++++++++++++++++------
 src/libventi/send.c    | 47 +++++++++++++++++++++++++++++++----------------
 src/libventi/version.c |  1 +
 6 files changed, 79 insertions(+), 23 deletions(-)

diff --git a/include/venti.h b/include/venti.h
index 8a64c57e..14627dcb 100644
--- a/include/venti.h
+++ b/include/venti.h
@@ -292,7 +292,7 @@ struct VtFcall
 	uint	nauth;		/* TauthX, RauthX */
 	uchar	score[VtScoreSize];	/* Tread, Rwrite */
 	uchar	blocktype;		/* Tread, Twrite */
-	ushort	count;		/* Tread */
+	uint	count;		/* Tread */
 	Packet	*data;		/* Rread, Twrite */
 };
 
diff --git a/man/man7/venti.7 b/man/man7/venti.7
index ae8fa65c..6f5826eb 100644
--- a/man/man7/venti.7
+++ b/man/man7/venti.7
@@ -441,6 +441,21 @@ message ends a session.  There is no
 upon receiving the
 .BR VtTgoodbye
 message, the server terminates up the connection.
+.PP
+Version
+.B 04
+of the Venti protocol is similar to version
+.B 02
+(described above)
+but has two changes to accomodates larger payloads.
+First, it replaces the leading 2-byte packet size with
+a 4-byte size.
+Second, the
+.I count
+in the
+.B VtTread
+packet may be either 2 or 4 bytes;
+the total packet length distinguishes the two cases.
 .SH SEE ALSO
 .IR venti (1),
 .IR venti (3),
diff --git a/src/libventi/client.c b/src/libventi/client.c
index 40ee8517..9f200f48 100644
--- a/src/libventi/client.c
+++ b/src/libventi/client.c
@@ -65,6 +65,10 @@ vtreadpacket(VtConn *z, uchar score[VtScoreSize], uint type, int n)
 	if(memcmp(score, vtzeroscore, VtScoreSize) == 0)
 		return packetalloc();
 
+	if(z->version[1] == '2' && n >= (1<<16)) {
+		werrstr("read count too large for protocol");
+		return nil;
+	}
 	memset(&tx, 0, sizeof tx);
 	tx.msgtype = VtTread;
 	tx.blocktype = type;
diff --git a/src/libventi/fcall.c b/src/libventi/fcall.c
index 65ee2d17..f2a03753 100644
--- a/src/libventi/fcall.c
+++ b/src/libventi/fcall.c
@@ -5,7 +5,7 @@
 Packet*
 vtfcallpack(VtFcall *f)
 {
-	uchar buf[4];
+	uchar buf[10];
 	Packet *p;
 
 	p = packetalloc();
@@ -60,9 +60,17 @@ vtfcallpack(VtFcall *f)
 		if(~buf[0] == 0)
 			goto Err;
 		buf[1] = 0;
-		buf[2] = f->count >> 8;
-		buf[3] = f->count;
-		packetappend(p, buf, 4);
+		if(f->count >= (1<<16)) {
+			buf[2] = f->count >> 24;
+			buf[3] = f->count >> 16;
+			buf[4] = f->count >> 8;
+			buf[5] = f->count;
+			packetappend(p, buf, 6);
+		} else {
+			buf[2] = f->count >> 8;
+			buf[3] = f->count;
+			packetappend(p, buf, 4);
+		}
 		break;
 
 	case VtRread:
@@ -163,12 +171,25 @@ vtfcallunpack(VtFcall *f, Packet *p)
 
 	case VtTread:
 		if(packetconsume(p, f->score, VtScoreSize) < 0
-		|| packetconsume(p, buf, 4) < 0)
+		|| packetconsume(p, buf, 2) < 0)
 			goto Err;
 		f->blocktype = vtfromdisktype(buf[0]);
 		if(~f->blocktype == 0)
 			goto Err;
-		f->count = (buf[2] << 8) | buf[3];
+		switch(packetsize(p)) {
+		default:
+			goto Err;
+		case 2:
+			if(packetconsume(p, buf, 2) < 0)
+				goto Err;
+			f->count = (buf[2] << 8) | buf[3];
+			break;
+		case 4:
+			if(packetconsume(p, buf, 4) < 0)
+				goto Err;
+			f->count = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
+			break;
+		}
 		break;
 
 	case VtRread:
diff --git a/src/libventi/send.c b/src/libventi/send.c
index 2b88818d..4dbe115f 100644
--- a/src/libventi/send.c
+++ b/src/libventi/send.c
@@ -11,7 +11,7 @@ _vtsend(VtConn *z, Packet *p)
 {
 	IOchunk ioc;
 	int n, tot;
-	uchar buf[2];
+	uchar buf[4];
 
 	if(z->state != VtStateConnected) {
 		werrstr("session not connected");
@@ -20,15 +20,24 @@ _vtsend(VtConn *z, Packet *p)
 
 	/* add framing */
 	n = packetsize(p);
-	if(n >= (1<<16)) {
-		werrstr("packet too large");
-		packetfree(p);
-		return -1;
+	if(z->version[1] == '2') {
+		if(n >= (1<<16)) {
+			werrstr("packet too large");
+			packetfree(p);
+			return -1;
+		}
+		buf[0] = n>>8;
+		buf[1] = n;
+		packetprefix(p, buf, 2);
+		ventisendbytes += n+2;
+	} else {
+		buf[0] = n>>24;
+		buf[1] = n>>16;
+		buf[2] = n>>8;
+		buf[3] = n;
+		packetprefix(p, buf, 4);
+		ventisendbytes += n+4;
 	}
-	buf[0] = n>>8;
-	buf[1] = n;
-	packetprefix(p, buf, 2);
-	ventisendbytes += n+2;
 	ventisendpackets++;
 
 	tot = 0;
@@ -63,7 +72,7 @@ static Packet*
 _vtrecv(VtConn *z)
 {
 	uchar buf[10], *b;
-	int n;
+	int n, need;
 	Packet *p;
 	int size, len;
 
@@ -75,11 +84,12 @@ _vtrecv(VtConn *z)
 	p = z->part;
 	/* get enough for head size */
 	size = packetsize(p);
-	while(size < 2) {
-		b = packettrailer(p, 2);
+	need = z->version[1] - '0';	// 2 or 4
+	while(size < need) {
+		b = packettrailer(p, need);
 		assert(b != nil);
 		if(0) fprint(2, "%d read hdr\n", getpid());
-		n = read(z->infd, b, 2);
+		n = read(z->infd, b, need);
 		if(0) fprint(2, "%d got %d (%r)\n", getpid(), n);
 		if(n==0 || (n<0 && !interrupted()))
 			goto Err;
@@ -87,10 +97,15 @@ _vtrecv(VtConn *z)
 		packettrim(p, 0, size);
 	}
 
-	if(packetconsume(p, buf, 2) < 0)
+	if(packetconsume(p, buf, need) < 0)
 		goto Err;
-	len = (buf[0] << 8) | buf[1];
-	size -= 2;
+	if(z->version[1] == '2') {
+		len = (buf[0] << 8) | buf[1];
+		size -= 2;
+	} else {
+		len = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
+		size -= 4;
+	}
 
 	while(size < len) {
 		n = len - size;
diff --git a/src/libventi/version.c b/src/libventi/version.c
index fd1e2389..655dcb36 100644
--- a/src/libventi/version.c
+++ b/src/libventi/version.c
@@ -3,6 +3,7 @@
 #include <venti.h>
 
 static char *okvers[] = {
+	"04",
 	"02",
 	nil,
 };
-- 
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