nusb/rndis: avoid allocation on each transmission

The slack space for outgoing packets set to 44+16 bytes.

2 files changed, 9 insertions, 13 deletions

diff --git a/sys/src/cmd/nusb/ether/ether.c b/sys/src/cmd/nusb/ether/ether.c
index 4b8b61845..cc3116911 100644
--- a/sys/src/cmd/nusb/ether/ether.c
+++ b/sys/src/cmd/nusb/ether/ether.c
@@ -290,12 +290,12 @@ writeconndata(Req *r)
 		n = 60;
 
 	/* slack space for header and trailers */
-	n += 2*16;
+	n += 44+16;
 
 	b = allocb(n);
 
 	/* header space */
-	b->wp += 16;
+	b->wp += 44;
 	b->rp = b->wp;
 
 	/* copy in the ethernet packet */
diff --git a/sys/src/cmd/nusb/ether/rndis.c b/sys/src/cmd/nusb/ether/rndis.c
index 88e91a725..bc688d9b7 100644
--- a/sys/src/cmd/nusb/ether/rndis.c
+++ b/sys/src/cmd/nusb/ether/rndis.c
@@ -95,19 +95,15 @@ static void
 rndistransmit(Dev *ep, Block *b)
 {
 	int n;
-	uchar *req;
 
 	n = BLEN(b);
-	if((req = malloc(44 + n)) != nil){
-		PUT4(req, 1);      /* type = 1 (packet) */
-		PUT4(req+4, 44+n); /* len */
-		PUT4(req+8, 44-8); /* data offset */
-		PUT4(req+12, n);   /* data length */
-		memset(req+16, 0, 7*4);
-		memcpy(req+44, b->rp, n);
-		write(ep->dfd, req, 44+n);
-		free(req);
-	}
+	b->rp -= 44;
+	PUT4(b->rp, 1);      /* type = 1 (packet) */
+	PUT4(b->rp+4, 44+n); /* len */
+	PUT4(b->rp+8, 44-8); /* data offset */
+	PUT4(b->rp+12, n);   /* data length */
+	memset(b->rp+16, 0, 7*4);
+	write(ep->dfd, b->rp, 44+n);
 	freeb(b);
 }