From: Roger Shimizu <rosh@debian.org>
Date: Sun, 6 Sep 2020 14:34:36 +0900
Subject: Make sla-len config optional

Cherry-pick from Fedora:
https://src.fedoraproject.org/rpms/wide-dhcpv6/blob/master/f/wide-dhcpv6-0008-Make-sla-len-config-optional.patch
---
 prefixconf.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/prefixconf.c b/prefixconf.c
index 15b5417..98d9b77 100644
--- a/prefixconf.c
+++ b/prefixconf.c
@@ -460,6 +460,17 @@ add_ifprefix(siteprefix, prefix, pconf)
 	ifpfx->paddr.sin6_len = sizeof(struct sockaddr_in6);
 #endif
 	ifpfx->paddr.sin6_addr = prefix->addr;
+
+	/*
+         * dave (bevhost) thinks this should fix it rather than
+         * generare the error below "invalid prefix length"
+         * this way the sla-len can be left out of the config file
+         * and calculated when the prefix is received
+         */
+	if (prefix->plen + pconf->ifid_len + pconf->sla_len > 128) {
+		pconf->sla_len = 128 - pconf->ifid_len - prefix->plen;
+	}
+
 	ifpfx->plen = prefix->plen + pconf->sla_len;
 	/*
 	 * XXX: our current implementation assumes ifid len is a multiple of 8