--- libaitio/src/bpf.c	2013/06/25 08:45:50	1.1.2.7
+++ libaitio/src/bpf.c	2013/06/25 10:58:22	1.1.2.11
@@ -97,11 +97,19 @@ allocZCbuf(u_int len)
 int
 io_etherOpen(const char *csIface, int flags, int whdr, u_int *buflen, void **zcbuf)
 {
-	int n = 1, eth = -1;
+	int eth = -1;
 	register int i;
 	char szStr[STRSIZ];
 	struct ifreq ifr;
+	u_int n = 1;
 
+#ifndef __FreeBSD__
+	if (zcbuf) {
+		io_SetErr(ENOTSUP, "bpf zero copy buffer mode is not supported");
+		return -1;
+	}
+#endif
+
 	for (i = 0; i < BPF_DEV_MAX; i++) {
 		memset(szStr, 0, sizeof szStr);
 		snprintf(szStr, sizeof szStr, "/dev/bpf%d", i);
@@ -124,45 +132,56 @@ io_etherOpen(const char *csIface, int flags, int whdr,
 		close(eth);
 		return -1;
 	}
-	if (buflen && *buflen) {
-		if (!zcbuf) {
-			if (ioctl(eth, BIOCSBLEN, buflen) == -1) {
-				LOGERR;
-				close(eth);
-				return -1;
-			}
-		} else {
+
+	if (!zcbuf) {
+		if (ioctl(eth, BIOCGBLEN, &n) == -1) {
+			LOGERR;
+			close(eth);
+			return -1;
+		} else
+			n = (buflen && *buflen) ? MIN(n, *buflen) : n;
+		if (ioctl(eth, BIOCSBLEN, &n) == -1) {
+			LOGERR;
+			close(eth);
+			return -1;
+		}
+		if (buflen && *buflen)
+			*buflen = n;
+	} else {
 #ifdef __FreeBSD__
-			n = BPF_BUFMODE_ZBUF;
-			if (ioctl(eth, BIOCSETBUFMODE, &n) == -1) {
-				LOGERR;
-				close(eth);
-				return -1;
-			}
-			if (ioctl(eth, BIOCGETZMAX, &n) == -1) {
-				LOGERR;
-				close(eth);
-				return -1;
-			} else
-				*buflen = MIN(n, *buflen);
-			if (!(*zcbuf = allocZCbuf(*buflen))) {
-				close(eth);
-				return -1;
-			}
-			if (ioctl(eth, BIOCSETZBUF, (struct bpf_zbuf*) *zcbuf) == -1) {
-				LOGERR;
-				io_etherClose(eth, zcbuf);
-				return -1;
-			}
-#endif
+		n = BPF_BUFMODE_ZBUF;
+		if (ioctl(eth, BIOCSETBUFMODE, &n) == -1) {
+			LOGERR;
+			close(eth);
+			return -1;
 		}
+		if (ioctl(eth, BIOCGETZMAX, &n) == -1) {
+			LOGERR;
+			close(eth);
+			return -1;
+		} else
+			n = (buflen && *buflen) ? MIN(n, *buflen) : n;
+		if (!(*zcbuf = allocZCbuf(n))) {
+			close(eth);
+			return -1;
+		}
+		if (ioctl(eth, BIOCSETZBUF, (struct bpf_zbuf*) *zcbuf) == -1) {
+			LOGERR;
+			io_etherClose(eth, zcbuf);
+			return -1;
+		}
+		if (buflen && *buflen)
+			*buflen = n;
+#endif
 	}
+
 	if (csIface)
 		strlcpy(szStr, csIface, sizeof szStr);
 	else if (io_get1stiface(szStr, sizeof szStr) == -1) {
 		io_etherClose(eth, zcbuf);
 		return -1;
 	}
+	memset(&ifr, 0, sizeof ifr);
 	strlcpy(ifr.ifr_name, szStr, sizeof ifr.ifr_name);
 	if (ioctl(eth, BIOCSETIF, &ifr) == -1) {
 		LOGERR;
@@ -198,6 +217,19 @@ 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, 
 		const void * __restrict buf)
@@ -207,20 +239,24 @@ nextZCbuf(void ** __restrict zcache, struct bpf_zbuf *
 
 	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
+			io_SetErr(EAGAIN, "kernel owns the buffer");
 	} 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);
+		} else
+			io_SetErr(EAGAIN, "kernel owns the buffer");
 	}
 
 	return rlen;