From 9e257558e2b1e0746659862ae054f6c62c79f1f5 Mon Sep 17 00:00:00 2001 From: florian Date: Mon, 13 Dec 2021 16:12:10 +0000 Subject: [PATCH] Only generate a new xid on state change. When we first request a lease (INIT or REBOOTING state) we run with very short timeouts. If the dhcp server is slow to respond we already have a new xid and ignore the server's response. This goes on until we increase the timeout high enough. If we just stick to an xid this will not happen and we accept "late" responses. RFC 2131 has: Selecting a new 'xid' for each retransmission is an implementation decision. A client may choose to reuse the same 'xid' or select a new 'xid' for each retransmitted message. Problem seen by phessler on german train wifi. OK phessler --- sbin/dhcpleased/engine.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/sbin/dhcpleased/engine.c b/sbin/dhcpleased/engine.c index 7c7cb458c4f..39eca76924e 100644 --- a/sbin/dhcpleased/engine.c +++ b/sbin/dhcpleased/engine.c @@ -1,4 +1,4 @@ -/* $OpenBSD: engine.c,v 1.32 2021/12/13 11:03:23 florian Exp $ */ +/* $OpenBSD: engine.c,v 1.33 2021/12/13 16:12:10 florian Exp $ */ /* * Copyright (c) 2017, 2021 Florian Obser @@ -616,6 +616,7 @@ engine_update_iface(struct imsg_ifinfo *imsg_ifinfo) if ((iface = calloc(1, sizeof(*iface))) == NULL) fatal("calloc"); iface->state = IF_DOWN; + iface->xid = arc4random(); iface->timo.tv_usec = arc4random_uniform(1000000); evtimer_set(&iface->timer, iface_timeout, iface); iface->if_index = imsg_ifinfo->if_index; @@ -1309,6 +1310,9 @@ state_transition(struct dhcpleased_iface *iface, enum if_state new_state) char ifnamebuf[IF_NAMESIZE], *if_name; iface->state = new_state; + if (new_state != old_state) + iface->xid = arc4random(); + switch (new_state) { case IF_DOWN: if (iface->requested_ip.s_addr == INADDR_ANY) { @@ -1468,7 +1472,6 @@ request_dhcp_discover(struct dhcpleased_iface *iface) memset(&imsg, 0, sizeof(imsg)); - iface->xid = arc4random(); imsg.if_index = iface->if_index; imsg.xid = iface->xid; @@ -1495,7 +1498,6 @@ request_dhcp_request(struct dhcpleased_iface *iface) { struct imsg_req_dhcp imsg; - iface->xid = arc4random(); imsg.if_index = iface->if_index; imsg.xid = iface->xid; -- 2.20.1