--- libaitio/src/bpf.c	2013/06/25 08:18:57	1.1.2.6
+++ libaitio/src/bpf.c	2013/06/25 08:53:22	1.1.2.8
@@ -198,23 +198,43 @@ io_etherSend(int eth, const void *buf, size_t buflen)
 }
 
 #ifdef __FreeBSD__
+static inline void
+ackZCbuf(struct bpf_zbuf_header * __restrict bzh)
+{
+	atomic_store_rel_int(&bzh->bzh_user_gen, bzh->bzh_kernel_gen);
+}
+
+static inline int
+chkZCbuf(struct bpf_zbuf_header * __restrict bzh)
+{
+	/* return true if userspace owns buffer, and false otherwise. */
+	return (bzh->bzh_user_gen != atomic_load_acq_int(&bzh->bzh_kernel_gen));
+}
+
 static inline ssize_t
-nextZCbuf(void ** __restrict zcache, struct bpf_zbuf * __restrict zbuf)
+nextZCbuf(void ** __restrict zcache, struct bpf_zbuf * __restrict zbuf, 
+		const void * __restrict buf)
 {
 	ssize_t rlen = -1;
 	struct bpf_zbuf_header *bzh;
 
 	if (!*zcache || *zcache == zbuf->bz_bufb) {
 		bzh = (struct bpf_zbuf_header *) zbuf->bz_bufa;
-		if (bzh->bzh_user_gen != atomic_load_acq_int(&bzh->bzh_kernel_gen)) {
+		if (chkZCbuf(bzh)) {
 			rlen = atomic_load_acq_int(&bzh->bzh_kernel_len);
 			*zcache = zbuf->bz_bufa;
+			if (buf)
+				buf = ((caddr_t) *zcache) + sizeof(struct bpf_zbuf_header);
+			ackZCbuf(bzh);
 		}
 	} else if (*zcache == zbuf->bz_bufa) {
 		bzh = (struct bpf_zbuf_header *) zbuf->bz_bufb;
-		if (bzh->bzh_user_gen != atomic_load_acq_int(&bzh->bzh_kernel_gen)) {
+		if (chkZCbuf(bzh)) {
 			rlen = atomic_load_acq_int(&bzh->bzh_kernel_len);
 			*zcache = zbuf->bz_bufb;
+			if (buf)
+				buf = ((caddr_t) *zcache) + sizeof(struct bpf_zbuf_header);
+			ackZCbuf(bzh);
 		}
 	}
 
@@ -248,8 +268,7 @@ io_etherRecv(int eth, void * __restrict buf, size_t bu
 			LOGERR;
 	} else {
 #ifdef __FreeBSD__
-		rlen = nextZCbuf(zcache, (struct bpf_zbuf*) zcbuf);
-		buf = *zcache;
+		rlen = nextZCbuf(zcache, (struct bpf_zbuf*) zcbuf, buf);
 #else
 		io_SetErr(ENOTSUP, "bpf zero copy buffer mode is not supported");
 #endif