Add NR_TX/RX_RINGS_ONLY flags

Add NR_TX_RINGS_ONLY and NR_RX_RINGS_ONLY flags which allow to request
only tx or rx hw rings.

Author: jibi

sys/dev/netmap/netmap.c

@@ -1730,6 +1730,12 @@ netmap_interp_ringid(struct netmap_priv_d *priv, uint16_t ringid, uint32_t flags
 	case NR_REG_PIPE_MASTER:
 	case NR_REG_PIPE_SLAVE:
 		for_rx_tx(t) {
+			if ((t == NR_RX && (flags & NR_TX_RINGS_ONLY)) ||
+			    (t == NR_TX && (flags & NR_RX_RINGS_ONLY))) {
+				priv->np_qfirst[t] = priv->np_qlast[t] = 0;
+				continue;
+			}
+
 			priv->np_qfirst[t] = 0;
 			priv->np_qlast[t] = nma_get_nrings(na, t);
 		}
@@ -1743,6 +1749,18 @@ netmap_interp_ringid(struct netmap_priv_d *priv, uint16_t ringid, uint32_t flags
 			return EINVAL;
 		}
 		for_rx_tx(t) {
+			if ((t == NR_RX && (flags & NR_TX_RINGS_ONLY)) ||
+			    (t == NR_TX && (flags & NR_RX_RINGS_ONLY))) {
+				/*
+				 * NR_[TX|RX]_RINGS_ONLY affects only hw
+				 * rings, so keep sw rings on in any
+				 * case
+				 */
+				priv->np_qfirst[t] = nma_get_nrings(na, t);
+				priv->np_qlast[t] = nma_get_nrings(na, t) + 1;
+				continue;
+			}
+
 			priv->np_qfirst[t] = (reg == NR_REG_SW ?
 				nma_get_nrings(na, t) : 0);
 			priv->np_qlast[t] = nma_get_nrings(na, t) + 1;
@@ -1756,6 +1774,12 @@ netmap_interp_ringid(struct netmap_priv_d *priv, uint16_t ringid, uint32_t flags
 			return EINVAL;
 		}
 		for_rx_tx(t) {
+			if ((t == NR_RX && (flags & NR_TX_RINGS_ONLY)) ||
+			    (t == NR_TX && (flags & NR_RX_RINGS_ONLY))) {
+				priv->np_qfirst[t] = priv->np_qlast[t] = 0;
+				continue;
+			}
+
 			/* if not enough rings, use the first one */
 			j = i;
 			if (j >= nma_get_nrings(na, t))

sys/net/netmap.h

@@ -532,6 +532,8 @@ enum {	NR_REG_DEFAULT	= 0,	/* backward compat, should not be used. */
 /* request ptnetmap host support */
 #define NR_PASSTHROUGH_HOST	NR_PTNETMAP_HOST /* deprecated */
 #define NR_PTNETMAP_HOST	0x1000
+#define NR_RX_RINGS_ONLY	0x2000
+#define NR_TX_RINGS_ONLY	0x4000
 
 
 /*

sys/net/netmap_user.h

@@ -313,6 +313,8 @@ typedef void (*nm_cb_t)(u_char *, const struct nm_pkthdr *, const u_char *d);
  *		z		zero copy monitor
  *		t		monitor tx side
  *		r		monitor rx side
+ *		R		bind only RX ring(s)
+ *		T		bind only TX ring(s)
  *
  * req		provides the initial values of nmreq before parsing ifname.
  *		Remember that the ifname parsing will override the ring
@@ -701,6 +703,12 @@ nm_open(const char *ifname, const struct nmreq *req,
 			case 'r':
 				nr_flags |= NR_MONITOR_RX;
 				break;
+			case 'R':
+				nr_flags |= NR_RX_RINGS_ONLY;
+				break;
+			case 'T':
+				nr_flags |= NR_TX_RINGS_ONLY;
+				break;
 			default:
 				snprintf(errmsg, MAXERRMSG, "unrecognized flag: '%c'", *port);
 				goto fail;