NetworkManager/SOURCES/1004-n-dhcp4-discard-NAKs-from-other-servers-rhbz2059673.patch
2022-05-10 11:03:03 +00:00

83 lines
3.5 KiB
Diff

From 118561e284ff7f28421b19530d4471075b89645c Mon Sep 17 00:00:00 2001
From: Beniamino Galvani <bgalvani@redhat.com>
Date: Thu, 10 Mar 2022 12:07:49 +0100
Subject: [PATCH] n-dhcp4: discard NAKs from other servers in SELECTING
I got a report of a scenario where multiple servers reply to a REQUEST
in SELECTING, and all servers send NAKs except the one which sent the
offer, which replies with a ACK. In that scenario, n-dhcp4 is not able
to obtain a lease because it restarts from INIT as soon as the first
NAK is received. For comparison, dhclient can get a lease because it
ignores all NAKs in SELECTING.
Arguably, the network is misconfigured there, but it would be great if
n-dhcp4 could still work in such scenario.
According to RFC 2131, ACK and NAK messages from server must contain a
server-id option. The RFC doesn't explicitly say that the client
should check the option, but I think it's a reasonable thing to do, at
least for NAKs.
This patch stores the server-id of the REQUEST in SELECTING, and
compares it with the server-id from NAKs, to discard other servers'
replies.
https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1144
---
src/n-dhcp4/src/n-dhcp4-c-connection.c | 19 +++++++++++++++++++
src/n-dhcp4/src/n-dhcp4-private.h | 1 +
2 files changed, 20 insertions(+)
diff --git a/src/n-dhcp4/src/n-dhcp4-c-connection.c b/src/n-dhcp4/src/n-dhcp4-c-connection.c
index 4aba97393d..2f660e3b30 100644
--- a/src/n-dhcp4/src/n-dhcp4-c-connection.c
+++ b/src/n-dhcp4/src/n-dhcp4-c-connection.c
@@ -705,6 +705,7 @@ int n_dhcp4_c_connection_select_new(NDhcp4CConnection *connection,
message->userdata.start_time = offer->userdata.start_time;
message->userdata.base_time = offer->userdata.base_time;
message->userdata.client_addr = client.s_addr;
+ message->userdata.server_id = server.s_addr;
n_dhcp4_incoming_get_xid(offer, &xid);
n_dhcp4_outgoing_set_xid(message, xid);
@@ -1224,6 +1225,24 @@ int n_dhcp4_c_connection_dispatch_io(NDhcp4CConnection *connection,
serv_addr, sizeof(serv_addr)));
}
+ if (type == N_DHCP4_MESSAGE_NAK &&
+ connection->request->userdata.server_id != INADDR_ANY) {
+ struct in_addr server;
+
+ r = n_dhcp4_incoming_query_server_identifier(message, &server);
+ if (r)
+ return N_DHCP4_E_AGAIN;
+
+ if (connection->request->userdata.server_id != server.s_addr) {
+ n_dhcp4_log(connection->log_queue,
+ LOG_DEBUG,
+ "discarded NAK with wrong server-id %s",
+ inet_ntop(AF_INET, &server,
+ serv_addr, sizeof(serv_addr)));
+ return N_DHCP4_E_AGAIN;
+ }
+ }
+
switch (type) {
case N_DHCP4_MESSAGE_OFFER:
case N_DHCP4_MESSAGE_ACK:
diff --git a/src/n-dhcp4/src/n-dhcp4-private.h b/src/n-dhcp4/src/n-dhcp4-private.h
index db7b24ff7d..191e946e70 100644
--- a/src/n-dhcp4/src/n-dhcp4-private.h
+++ b/src/n-dhcp4/src/n-dhcp4-private.h
@@ -202,6 +202,7 @@ struct NDhcp4Outgoing {
uint8_t type;
uint8_t message_type;
uint32_t client_addr;
+ uint32_t server_id;
uint64_t start_time;
uint64_t base_time;
uint64_t send_time;
--
2.35.1