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dhcp: truncate client-id for n-dhcp4 client at arbitrary limit

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RFC does not define how long the client ID can be. However,
n-dhcp4 enforces that the server replies with a client ID that
matches the request. Also, the client ID gets encoded as a DHCP
option, hence it cannot be longer than 255 bytes.

While n-dhcp4 doesn't enforce a certain length, a too long client
ID is not going to work. Hence, truncate it at 133 bytes.

This is the same limit that also systemd's DHCP client has. It's chosen
to fit an RFC4361-complient client ID with a DUID of length
MAX_DUID_LEN (which is 128 bytes according to RFC 3315 section 9.1).

Fixes-test: @ipv4_set_very_long_dhcp_client_id

See-also: https://github.com/nettools/n-dhcp4/pull/6

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/merge_requests/307
This commit is contained in:
Thomas Haller 2019-10-14 12:35:30 +02:00
parent 907bd28203
commit 7efc3c479f
1 changed files with 3 additions and 1 deletions
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4
src/dhcp/nm-dhcp-nettools.c
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@ -1096,7 +1096,9 @@ nettools_create (NMDhcpNettools *self,
n_dhcp4_client_config_set_transport (config, transport);
n_dhcp4_client_config_set_mac (config, hwaddr_arr, hwaddr_len);
n_dhcp4_client_config_set_broadcast_mac (config, bcast_hwaddr_arr, bcast_hwaddr_len);
r = n_dhcp4_client_config_set_client_id (config, client_id_arr, client_id_len);
r = n_dhcp4_client_config_set_client_id (config,
client_id_arr,
NM_MIN (client_id_len, 1 + _NM_SD_MAX_CLIENT_ID_LEN));
if (r) {
nm_utils_error_set_errno (error, r, "failed to set client-id: %s");
return FALSE;