selftests/bpf: Implement set_hw_ring_size function to configure interface ring size

Introduce a new function called set_hw_ring_size that allows for the
dynamic configuration of the ring size within the interface.
Signed-off-by: Tushar Vyavahare <tushar.vyavahare@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20240402114529.545475-5-tushar.vyavahare@intel.com

tools/testing/selftests/bpf/network_helpers.c

@@ -521,3 +521,27 @@ int get_hw_ring_size(char *ifname, struct ethtool_ringparam *ring_param)
 	close(sockfd);
 	return 0;
 }
+
+int set_hw_ring_size(char *ifname, struct ethtool_ringparam *ring_param)
+{
+	struct ifreq ifr = {0};
+	int sockfd, err;
+
+	sockfd = socket(AF_INET, SOCK_DGRAM, 0);
+	if (sockfd < 0)
+		return -errno;
+
+	memcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
+
+	ring_param->cmd = ETHTOOL_SRINGPARAM;
+	ifr.ifr_data = (char *)ring_param;
+
+	if (ioctl(sockfd, SIOCETHTOOL, &ifr) < 0) {
+		err = errno;
+		close(sockfd);
+		return -err;
+	}
+
+	close(sockfd);
+	return 0;
+}

tools/testing/selftests/bpf/network_helpers.h

@@ -65,6 +65,7 @@ int make_sockaddr(int family, const char *addr_str, __u16 port,
 char *ping_command(int family);
 int get_socket_local_port(int sock_fd);
 int get_hw_ring_size(char *ifname, struct ethtool_ringparam *ring_param);
+int set_hw_ring_size(char *ifname, struct ethtool_ringparam *ring_param);
 
 struct nstoken;
 /**