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Fix migrate_sonic_packages() crash on symlink resolv.conf #4365

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Merged
yxieca merged 1 commit into from
Mar 20, 2026
+18 −7
Merged

Fix migrate_sonic_packages() crash on symlink resolv.conf #4365

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17 changes: 13 additions & 4 deletions sonic_installer/main.py
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Original file line number Diff line number Diff line change
Expand Up @@ -325,7 +325,6 @@ def migrate_sonic_packages(bootloader, binary_image_version):
DOCKERD_SOCK = "docker.sock"
VAR_RUN_PATH = "/var/run/"
RESOLV_CONF_FILE = os.path.join("etc", "resolv.conf")
RESOLV_CONF_BACKUP_FILE = os.path.join("/", TMP_DIR, "resolv.conf.backup")

packages_file = "packages.json"
packages_path = os.path.join(PACKAGE_MANAGER_DIR, packages_file)
Expand Down Expand Up @@ -382,8 +381,19 @@ def migrate_sonic_packages(bootloader, binary_image_version):
os.path.join(VAR_RUN_PATH, DOCKERD_SOCK),
os.path.join(new_image_mount, "tmp", DOCKERD_SOCK)])

run_command_or_raise(["cp", os.path.join(new_image_mount, RESOLV_CONF_FILE), RESOLV_CONF_BACKUP_FILE])
run_command_or_raise(["cp", os.path.join("/", RESOLV_CONF_FILE), os.path.join(new_image_mount, RESOLV_CONF_FILE)])
# Inject host DNS into chroot for sonic-package-manager to resolve hostnames.
chroot_resolv = os.path.join(new_image_mount, RESOLV_CONF_FILE)
if os.path.islink(chroot_resolv):
# Symlink: populate the target inside the chroot so the symlink resolves.
# Cannot cp over the symlink because the absolute target path escapes
# the overlay mount to the host filesystem ("are the same file" error).
resolv_target = os.readlink(chroot_resolv)
chroot_target = os.path.join(new_image_mount, resolv_target.lstrip("/"))
run_command_or_raise(["mkdir", "-p", os.path.dirname(chroot_target)])
run_command_or_raise(["cp", "-L", os.path.join("/", RESOLV_CONF_FILE), chroot_target])
else:
# Regular file: overwrite with host DNS content.
run_command_or_raise(["cp", os.path.join("/", RESOLV_CONF_FILE), chroot_resolv])

run_command_or_raise(["chroot", new_image_mount, "sh", "-c", "command -v {}".format(SONIC_PACKAGE_MANAGER)])
run_command_or_raise(["chroot", new_image_mount, SONIC_PACKAGE_MANAGER, "migrate",
Expand All @@ -395,7 +405,6 @@ def migrate_sonic_packages(bootloader, binary_image_version):
run_command_or_raise(["chroot", new_image_mount, DOCKER_CTL_SCRIPT, "stop"], raise_exception=False)
if os.path.exists(docker_default_config_backup):
run_command_or_raise(["mv", docker_default_config_backup, docker_default_config], raise_exception=False);
run_command_or_raise(["cp", RESOLV_CONF_BACKUP_FILE, os.path.join(new_image_mount, RESOLV_CONF_FILE)], raise_exception=False)
umount(new_image_mount, recursive=True, read_only=False, remove_dir=False, raise_exception=False)
umount(new_image_mount, raise_exception=False)

Expand Down
8 changes: 5 additions & 3 deletions tests/test_sonic_installer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,8 @@ def test_install(run_command, run_command_or_raise, get_bootloader, swap, fs):
fs.create_dir(os.path.join(mounted_image_folder, "usr/lib/docker/docker.sh"))
fs.create_file("/var/run/docker.pid", contents="15")
fs.create_file("/proc/15/cmdline", contents="\x00".join(["dockerd"] + dockerd_opts))
# Simulate new image: /etc/resolv.conf is a dangling symlink (target doesn't exist in squashfs)
fs.create_symlink(f"{mounted_image_folder}/etc/resolv.conf", "/run/resolvconf/resolv.conf")

# Setup bootloader mock
mock_bootloader = Mock()
Expand Down Expand Up @@ -91,12 +93,12 @@ def rootfs_path_mock(path):
f"{mounted_image_folder}/var/lib/sonic-package-manager"]),
call(["touch", f"{mounted_image_folder}/tmp/docker.sock"]),
call(["mount", "--bind", "/var/run/docker.sock", f"{mounted_image_folder}/tmp/docker.sock"]),
call(["cp", f"{mounted_image_folder}/etc/resolv.conf", "/tmp/resolv.conf.backup"]),
call(["cp", "/etc/resolv.conf", f"{mounted_image_folder}/etc/resolv.conf"]),
# /etc/resolv.conf is a dangling symlink -> /run/resolvconf/resolv.conf, populate its target
call(["mkdir", "-p", f"{mounted_image_folder}/run/resolvconf"]),
call(["cp", "-L", "/etc/resolv.conf", f"{mounted_image_folder}/run/resolvconf/resolv.conf"]),
call(["chroot", mounted_image_folder, "sh", "-c", "command -v sonic-package-manager"]),
call(["chroot", mounted_image_folder, "sonic-package-manager", "migrate", "/tmp/packages.json", "--dockerd-socket", "/tmp/docker.sock", "-y"], capture=False),
call(["chroot", mounted_image_folder, "/usr/lib/docker/docker.sh", "stop"], raise_exception=False),
call(["cp", "/tmp/resolv.conf.backup", f"{mounted_image_folder}/etc/resolv.conf"], raise_exception=False),
call(["umount", "-f", "-R", mounted_image_folder], raise_exception=False),
call(["umount", "-r", "-f", mounted_image_folder], raise_exception=False),
call(["rm", "-rf", mounted_image_folder], raise_exception=False),
Expand Down
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