Debian package portmap 6.0.0-5 in experimental has patch 06-615642-reuse-socket.diff that makes portmap set SO_REUSEADDR. I do not understand what the LOOPBACK_SETUNSET #define actually do, but it basically removes it.
It's also worth noting that rpcbind suffers from bug #924593, which is quite similar and that upstream resolved by setting the SO_REUSEADDR option.
Debian package portmap 6.0.0-5 in experimental has patch 06-615642- reuse-socket. diff that makes portmap set SO_REUSEADDR. I do not understand what the LOOPBACK_SETUNSET #define actually do, but it basically removes it.
It's also worth noting that rpcbind suffers from bug #924593, which is quite similar and that upstream resolved by setting the SO_REUSEADDR option.