drivers: nsos: support ioctl(FIONREAD)

This further increases compatibility with tests defined in
'tests/net/socket/udp/'.

Signed-off-by: Marcin Niestroj <m.niestroj@emb.dev>

drivers/net/nsos.h

@@ -138,6 +138,8 @@ void nsos_adapt_poll_update(struct nsos_mid_pollfd *pollfd);
 int nsos_adapt_fcntl_getfl(int fd);
 int nsos_adapt_fcntl_setfl(int fd, int flags);
 
+int nsos_adapt_fionread(int fd, int *avail);
+
 int nsos_adapt_getaddrinfo(const char *node, const char *service,
 			   const struct nsos_mid_addrinfo *hints,
 			   struct nsos_mid_addrinfo **res,

drivers/net/nsos_adapt.c

@@ -20,6 +20,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/epoll.h>
+#include <sys/ioctl.h>
 #include <sys/socket.h>
 #include <unistd.h>
 
@@ -939,6 +940,18 @@ int nsos_adapt_fcntl_setfl(int fd, int flags)
 	return 0;
 }
 
+int nsos_adapt_fionread(int fd, int *avail)
+{
+	int ret;
+
+	ret = ioctl(fd, FIONREAD, avail);
+	if (ret < 0) {
+		return -errno_to_nsos_mid(errno);
+	}
+
+	return 0;
+}
+
 static void nsos_adapt_init(void)
 {
 	nsos_epoll_fd = epoll_create(1);

drivers/net/nsos_sockets.c

@@ -371,6 +371,15 @@ static int nsos_ioctl(void *obj, unsigned int request, va_list args)
 
 		return -errno_from_nsos_mid(-ret);
 	}
+
+	case ZFD_IOCTL_FIONREAD: {
+		int *avail = va_arg(args, int *);
+		int ret;
+
+		ret = nsos_adapt_fionread(sock->pollfd.fd, avail);
+
+		return -errno_from_nsos_mid(-ret);
+	}
 	}
 
 	return -EINVAL;