[PATCH 2/3] shared/net-util-linux: add support for retrieving NIC h/w queues

[Nilay Shroff]

Add a new shared helper, shr_netdev_get_hw_queues(), which retrieves the
NIC h/w queue details using ethtool ioctl ETHTOOL_GCHANNELS.

This is a preparatory patch. A subsequent patch will use this helper
to determine the h/w queue details when calculating the default
--nr-io-queues value for NVMe/TCP connections.

Signed-off-by: Nilay Shroff <nilay at linux.ibm.com>
---
 shared/net-util-linux.c | 37 +++++++++++++++++++++++++++++++++++++
 shared/net-util.h       | 16 ++++++++++++++++
 2 files changed, 53 insertions(+)

diff --git a/shared/net-util-linux.c b/shared/net-util-linux.c
index 887755ce9..7517fccbe 100644
--- a/shared/net-util-linux.c
+++ b/shared/net-util-linux.c
@@ -9,13 +9,16 @@
 #include <arpa/inet.h>
 #include <asm/types.h>
 #include <errno.h>
+#include <linux/ethtool.h>
 #include <linux/netlink.h>
 #include <linux/rtnetlink.h>
+#include <linux/sockios.h>
 #include <net/if.h>
 #include <netinet/in.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <sys/ioctl.h>
 #include <sys/socket.h>
 #include <unistd.h>
 
@@ -409,3 +412,37 @@ out:
 	close(fd);
 	return ret;
 }
+
+int shr_netdev_get_hw_queues(const char *ifname, uint32_t *combined_count,
+		uint32_t *tx_count, uint32_t *rx_count)
+{
+	struct ethtool_channels chan = {};
+	struct ifreq ifr = {};
+	int fd, ret = 0;
+
+	if (!ifname || !combined_count || !tx_count || !rx_count)
+		return -EINVAL;
+
+	fd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (fd < 0) {
+		fprintf(stderr, "opening socket failed\n");
+		return -errno;
+	}
+
+	chan.cmd = ETHTOOL_GCHANNELS;
+	snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", ifname);
+	ifr.ifr_data = (void *)&chan;
+
+	if (ioctl(fd, SIOCETHTOOL, &ifr) < 0) {
+		fprintf(stderr, "SIOCETHTOOL failed\n");
+		ret = -errno;
+		goto out;
+	}
+
+	*combined_count = chan.combined_count;
+	*tx_count = chan.tx_count;
+	*rx_count = chan.rx_count;
+out:
+	close(fd);
+	return ret;
+}
diff --git a/shared/net-util.h b/shared/net-util.h
index 0208923e5..59d201210 100644
--- a/shared/net-util.h
+++ b/shared/net-util.h
@@ -8,6 +8,7 @@
 #pragma once
 
 #include <ifaddrs.h>
+#include <inttypes.h>
 #include <stdbool.h>
 
 /*
@@ -64,3 +65,18 @@ bool shr_iface_primary_addr_matches(const struct ifaddrs *iface_list,
  */
 int shr_route_get_egress_iface(const char *saddr, const char *daddr,
 		char *ifname, size_t iflen);
+
+/*
+ * shr_netdev_get_hw_queues - Get h/w queues details for a netdevice
+ *
+ * @ifname: Name of network interface
+ * @combined_count: combined h/w queue count
+ * @tx_count: tx queue count
+ * @rx_count: rx queue count
+ *
+ * Retrieves the NIC h/w queue details.
+ *
+ * Return: 0 on success and negative errno on failure.
+ */
+int shr_netdev_get_hw_queues(const char *ifname, uint32_t *combined_count,
+		uint32_t *tx_count, uint32_t *rx_count);
-- 
2.53.0