From d88e4d82efc7aca47f1e31808717c9718e466d93 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 4 Aug 2016 16:24:28 +1000 Subject: SUNRPC: disable the use of IPv6 temporary addresses. If the net.ipv6.conf.*.use_temp_addr sysctl is set to '2', then TCP connections over IPv6 will prefer a 'private' source address. These eventually expire and become invalid, typically after a week, but the time is configurable. When the local address becomes invalid the client will not be able to receive replies from the server. Eventually the connection will timeout or break and a new connection will be established, but this can take half an hour (typically TCP connection break time). RFC 4941, which describes private IPv6 addresses, acknowledges that some applications might not work well with them and that the application may explicitly a request non-temporary (i.e. "public") address. I believe this is correct for SUNRPC clients. Without this change, a client will occasionally experience a long delay if private addresses have been enabled. The privacy offered by private addresses is of little value for an NFS server which requires client authentication. For NFSv3 this will often not be a problem because idle connections are closed after 5 minutes. For NFSv4 connections never go idle due to the period RENEW (or equivalent) request. Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust --- net/sunrpc/xprtsock.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'net') diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index c6b1d48c4319..bf79212fdbf8 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -2236,6 +2236,7 @@ static int xs_tcp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock) unsigned int keepcnt = xprt->timeout->to_retries + 1; unsigned int opt_on = 1; unsigned int timeo; + unsigned int addr_pref = IPV6_PREFER_SRC_PUBLIC; /* TCP Keepalive options */ kernel_setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, @@ -2247,6 +2248,16 @@ static int xs_tcp_finish_connecting(struct rpc_xprt *xprt, struct socket *sock) kernel_setsockopt(sock, SOL_TCP, TCP_KEEPCNT, (char *)&keepcnt, sizeof(keepcnt)); + /* Avoid temporary address, they are bad for long-lived + * connections such as NFS mounts. + * RFC4941, section 3.6 suggests that: + * Individual applications, which have specific + * knowledge about the normal duration of connections, + * MAY override this as appropriate. + */ + kernel_setsockopt(sock, SOL_IPV6, IPV6_ADDR_PREFERENCES, + (char *)&addr_pref, sizeof(addr_pref)); + /* TCP user timeout (see RFC5482) */ timeo = jiffies_to_msecs(xprt->timeout->to_initval) * (xprt->timeout->to_retries + 1); -- cgit