Bug #40086 for dhcp-public: [PATCH] dhcrelay v6: No route to host

On OpenBSD 5.7, with ISC DHCP 4.3.2, the DHCP relay does not properly forward packets to the downstream interface, instead logging "send_packet6: No route to host". Indeed, a proper route to the host exists, and connectivity is confirmed. Instead, it appears that dhcrelay is not properly setting the sin6_scope_id for the outbound packet. An example follows: # sbin/dhcrelay -d -6 -l vlan3930 -u vlan3920 Internet Systems Consortium DHCP Relay Agent 4.3.2 Copyright 2004-2015 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Bound to *:547 Listening on Socket/vlan3920 Sending on Socket/vlan3920 Listening on Socket/vlan3930 Sending on Socket/vlan3930 Setting hop count limit to 32 for interface vlan3920 Relaying Solicit from fe80::fd8d:a178:51dd:601 port 546 going up. Relaying Advertise to fe80::fd8d:a178:51dd:601 port 546 down. send_packet6: No route to host Relaying Solicit from fe80::fd8d:a178:51dd:601 port 546 going up. Relaying Advertise to fe80::fd8d:a178:51dd:601 port 546 down. send_packet6: No route to host Relaying Solicit from fe80::fd8d:a178:51dd:601 port 546 going up. Relaying Advertise to fe80::fd8d:a178:51dd:601 port 546 down. send_packet6: No route to host Relaying Solicit from fe80::fd8d:a178:51dd:601 port 546 going up. Relaying Advertise to fe80::fd8d:a178:51dd:601 port 546 down. send_packet6: No route to host ---------- I was able to rectify the issue by modifying common/socket.c to set the sin6_scope_id in all cases: # diff -up common/socket.c.orig common/socket.c --- common/socket.c.orig Thu Jul 16 10:29:06 2015 +++ common/socket.c Thu Jul 16 10:29:52 2015 @@ -794,8 +794,7 @@ ssize_t send_packet6(struct interface_info *interface, m.msg_name = &dst; m.msg_namelen = sizeof(dst); ifindex = if_nametoindex(interface->name); - if (no_global_v6_socket) - dst.sin6_scope_id = ifindex; + dst.sin6_scope_id = ifindex; /* * Set the data buffer we're sending. (Using this wacky ---------- The patched dhcrelay works as expected: # sbin/dhcrelay -d -6 -l vlan3930 -u vlan3920 Internet Systems Consortium DHCP Relay Agent 4.3.2 Copyright 2004-2015 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Bound to *:547 Listening on Socket/vlan3920 Sending on Socket/vlan3920 Listening on Socket/vlan3930 Sending on Socket/vlan3930 Setting hop count limit to 32 for interface vlan3920 Relaying Solicit from fe80::fd8d:a178:51dd:601 port 546 going up. Relaying Advertise to fe80::fd8d:a178:51dd:601 port 546 down. Relaying Request from fe80::fd8d:a178:51dd:601 port 546 going up. Relaying Reply to fe80::fd8d:a178:51dd:601 port 546 down. Relaying Renew from fe80::fd8d:a178:51dd:601 port 546 going up. Relaying Reply to fe80::fd8d:a178:51dd:601 port 546 down. ---------- I do not know the consequences of always setting sin6_scope_id on the operation of dhclient or dhcpd, nor have I tested it on systems other than OpenBSD. Best, Vladimir Voskoboynikov

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