[OE-core] [PATCH] image.bbclass: add postprocess func to disable DNS lookups for openssh

[Stefan Stanacar]

In the default config openssh does reverse DNS resolution, but
if there is no DNS configured on the target (or even worse the
DNS server is unreachable) there is a long timeout when connecting
over ssh. This is most visible on core-image-sato-sdk builds on AB, where the
tests take a long time because each ssh command spends 15 seconds
just connecting to the target, disabling the reverse DNS resolution halves
the total test time.
This isn't a qemu specific problem however and instead of changing the default
config I think it's worth disabling this when debug-tweaks is enabled.

Patch based on a previous version sent by Saul Wold <sgw at linux.intel.com>

[YOCTO #5954]

Signed-off-by: Stefan Stanacar <stefanx.stanacar at intel.com>
---
 meta/classes/image.bbclass | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index 29309f5..846c768 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -146,6 +146,8 @@ MACHINE_POSTPROCESS_COMMAND ?= ""
 ROOTFS_POSTPROCESS_COMMAND += '${@base_contains("IMAGE_FEATURES", "debug-tweaks", "ssh_allow_empty_password; ", "",d)}'
 # Enable postinst logging if debug-tweaks is enabled
 ROOTFS_POSTPROCESS_COMMAND += '${@base_contains("IMAGE_FEATURES", "debug-tweaks", "postinst_enable_logging; ", "",d)}'
+# Disable DNS lookups if debug-tweaks is enabled
+ROOTFS_POSTPROCESS_COMMAND += '${@base_contains("IMAGE_FEATURES", "debug-tweaks", "ssh_disable_dns_lookup; ", "",d)}'
 # Write manifest
 IMAGE_MANIFEST = "${DEPLOY_DIR_IMAGE}/${IMAGE_NAME}.rootfs.manifest"
 ROOTFS_POSTPROCESS_COMMAND =+ "write_image_manifest ; "
@@ -304,6 +306,12 @@ ssh_allow_empty_password () {
 	fi
 }
 
+ssh_disable_dns_lookup () {
+        if [ -e ${IMAGE_ROOTFS}${sysconfdir}/ssh/sshd_config ]; then
+            sed -i -e 's:#UseDNS yes:UseDNS no:' ${IMAGE_ROOTFS}${sysconfdir}/ssh/sshd_config
+        fi
+}
+
 # Enable postinst logging if debug-tweaks is enabled
 postinst_enable_logging () {
 	mkdir -p ${IMAGE_ROOTFS}${sysconfdir}/default
@@ -374,7 +382,7 @@ rootfs_sysroot_relativelinks () {
 	sysroot-relativelinks.py ${SDK_OUTPUT}/${SDKTARGETSYSROOT}
 }
 
-EXPORT_FUNCTIONS zap_empty_root_password remove_init_link do_rootfs make_zimage_symlink_relative set_image_autologin rootfs_update_timestamp rootfs_no_x_startup
+EXPORT_FUNCTIONS zap_empty_root_password remove_init_link do_rootfs make_zimage_symlink_relative set_image_autologin rootfs_update_timestamp rootfs_no_x_startup ssh_disable_dns_lookup
 
 do_fetch[noexec] = "1"
 do_unpack[noexec] = "1"
-- 
1.9.0