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From 268080fc19990711a1d1e1acd68a50aa2f6cb5fb Mon Sep 17 00:00:00 2001
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From: =?UTF-8?q?Petr=20Men=C5=A1=C3=ADk?= <pemensik@redhat.com>
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Date: Fri, 17 Sep 2021 20:12:21 +0200
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Subject: [PATCH] Offer alternative DHCPv6 address if requested is taken
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In some cases multiple requests might arrive from single DUID. It may
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happen just one address is offered to different IAID requests. When
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the first request confirms lease, another would be offered alternative
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address instead of address in use error.
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Includes check on such Rapid commit equivalents and returns NotOnLink
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error, required by RFC 8145, if requested address were not on any
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supported prefix.
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---
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src/rfc3315.c | 39 ++++++++++++++++++++++++++++-----------
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1 file changed, 28 insertions(+), 11 deletions(-)
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diff --git a/src/rfc3315.c b/src/rfc3315.c
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index 5c2ff97..d1534ad 100644
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--- a/src/rfc3315.c
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+++ b/src/rfc3315.c
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@@ -614,7 +614,7 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
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case DHCP6SOLICIT:
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{
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- int address_assigned = 0;
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+ int address_assigned = 0, ia_invalid = 0;
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/* tags without all prefix-class tags */
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struct dhcp_netid *solicit_tags;
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struct dhcp_context *c;
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@@ -697,6 +697,8 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
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get_context_tag(state, c);
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address_assigned = 1;
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}
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+ else
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+ ia_invalid++;
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}
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/* Suggest configured address(es) */
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@@ -782,11 +784,26 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
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tagif = add_options(state, 0);
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}
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else
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- {
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+ {
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+ char *errmsg;
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/* no address, return error */
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o1 = new_opt6(OPTION6_STATUS_CODE);
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- put_opt6_short(DHCP6NOADDRS);
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- put_opt6_string(_("no addresses available"));
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+ if (state->lease_allocate && ia_invalid)
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+ {
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+ /* RFC 8415, Section 18.3.2:
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+ If any of the prefixes of the included addresses are not
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+ appropriate for the link to which the client is connected,
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+ the server MUST return the IA to the client with a Status
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+ Code option with the value NotOnLink. */
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+ put_opt6_short(DHCP6NOTONLINK);
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+ errmsg = _("not on link");
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+ }
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+ else
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+ {
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+ put_opt6_short(DHCP6NOADDRS);
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+ errmsg = _("no addresses available");
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+ }
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+ put_opt6_string(errmsg);
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end_opt6(o1);
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/* Some clients will ask repeatedly when we're not giving
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@@ -795,7 +812,7 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
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for (c = state->context; c; c = c->current)
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if (!(c->flags & CONTEXT_RA_STATELESS))
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{
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- log6_packet(state, state->lease_allocate ? "DHCPREPLY" : "DHCPADVERTISE", NULL, _("no addresses available"));
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+ log6_packet(state, state->lease_allocate ? "DHCPREPLY" : "DHCPADVERTISE", NULL, errmsg);
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break;
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}
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}
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@@ -831,7 +848,7 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
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/* If we get a request with an IA_*A without addresses, treat it exactly like
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a SOLICT with rapid commit set. */
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save_counter(start);
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- goto request_no_address;
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+ goto request_no_address;
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}
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o = build_ia(state, &t1cntr);
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@@ -861,11 +878,11 @@ static int dhcp6_no_relay(struct state *state, int msg_type, void *inbuff, size_
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}
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else if (!check_address(state, &req_addr))
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{
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- /* Address leased to another DUID/IAID */
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- o1 = new_opt6(OPTION6_STATUS_CODE);
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- put_opt6_short(DHCP6UNSPEC);
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- put_opt6_string(_("address in use"));
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- end_opt6(o1);
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+ /* Address leased to another DUID/IAID.
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+ Find another address for the client, treat it exactly like
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+ a SOLICT with rapid commit set. */
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+ save_counter(start);
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+ goto request_no_address;
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}
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else
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{
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--
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2.31.1
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