From 323a53c41292a0d7efc8748856c623324c8d7c21 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 5 Jun 2019 07:55:09 -0700 Subject: [PATCH] ipv6: tcp: enable flowlabel reflection in some RST packets When RST packets are sent because no socket could be found, it makes sense to use flowlabel_reflect sysctl to decide if a reflection of the flowlabel is requested. This extends commit 22b6722bfa59 ("ipv6: Add sysctl for per namespace flow label reflection"), for some TCP RST packets. In order to provide full control of this new feature, flowlabel_reflect becomes a bitmask. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- Documentation/networking/ip-sysctl.txt | 20 +++++++++++++++----- net/ipv6/af_inet6.c | 2 +- net/ipv6/sysctl_net_ipv6.c | 3 +++ net/ipv6/tcp_ipv6.c | 13 ++++++++++--- 4 files changed, 29 insertions(+), 9 deletions(-) diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index a73b3a02e49a..f4b1043e92ed 100644 --- a/Documentation/networking/ip-sysctl.txt +++ b/Documentation/networking/ip-sysctl.txt @@ -1429,14 +1429,24 @@ flowlabel_state_ranges - BOOLEAN FALSE: disabled Default: true -flowlabel_reflect - BOOLEAN - Automatically reflect the flow label. Needed for Path MTU +flowlabel_reflect - INTEGER + Control flow label reflection. Needed for Path MTU Discovery to work with Equal Cost Multipath Routing in anycast environments. See RFC 7690 and: https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01 - TRUE: enabled - FALSE: disabled - Default: FALSE + + This is a mask of two bits. + 1: enabled for established flows + + Note that this prevents automatic flowlabel changes, as done + in "tcp: change IPv6 flow-label upon receiving spurious retransmission" + and "tcp: Change txhash on every SYN and RTO retransmit" + + 2: enabled for TCP RESET packets (no active listener) + If set, a RST packet sent in response to a SYN packet on a closed + port will reflect the incoming flow label. + + Default: 0 fib_multipath_hash_policy - INTEGER Controls which hash policy to use for multipath routes. diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c index cc6f8d0c625a..ceab2fe2833b 100644 --- a/net/ipv6/af_inet6.c +++ b/net/ipv6/af_inet6.c @@ -212,7 +212,7 @@ lookup_protocol: np->mc_loop = 1; np->mc_all = 1; np->pmtudisc = IPV6_PMTUDISC_WANT; - np->repflow = net->ipv6.sysctl.flowlabel_reflect; + np->repflow = net->ipv6.sysctl.flowlabel_reflect & 1; sk->sk_ipv6only = net->ipv6.sysctl.bindv6only; /* Init the ipv4 part of the socket since we can have sockets diff --git a/net/ipv6/sysctl_net_ipv6.c b/net/ipv6/sysctl_net_ipv6.c index e15cd37024fd..6d86fac472e7 100644 --- a/net/ipv6/sysctl_net_ipv6.c +++ b/net/ipv6/sysctl_net_ipv6.c @@ -23,6 +23,7 @@ static int zero; static int one = 1; +static int three = 3; static int auto_flowlabels_min; static int auto_flowlabels_max = IP6_AUTO_FLOW_LABEL_MAX; @@ -114,6 +115,8 @@ static struct ctl_table ipv6_table_template[] = { .maxlen = sizeof(int), .mode = 0644, .proc_handler = proc_dointvec, + .extra1 = &zero, + .extra2 = &three, }, { .procname = "max_dst_opts_number", diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index beaf28456301..4ccb06ea8ce3 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -916,15 +916,17 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32 static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb) { const struct tcphdr *th = tcp_hdr(skb); + struct ipv6hdr *ipv6h = ipv6_hdr(skb); u32 seq = 0, ack_seq = 0; struct tcp_md5sig_key *key = NULL; #ifdef CONFIG_TCP_MD5SIG const __u8 *hash_location = NULL; - struct ipv6hdr *ipv6h = ipv6_hdr(skb); unsigned char newhash[16]; int genhash; struct sock *sk1 = NULL; #endif + __be32 label = 0; + struct net *net; int oif = 0; if (th->rst) @@ -936,6 +938,7 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb) if (!sk && !ipv6_unicast_destination(skb)) return; + net = dev_net(skb_dst(skb)->dev); #ifdef CONFIG_TCP_MD5SIG rcu_read_lock(); hash_location = tcp_parse_md5sig_option(th); @@ -949,7 +952,7 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb) * Incoming packet is checked with md5 hash with finding key, * no RST generated if md5 hash doesn't match. */ - sk1 = inet6_lookup_listener(dev_net(skb_dst(skb)->dev), + sk1 = inet6_lookup_listener(net, &tcp_hashinfo, NULL, 0, &ipv6h->saddr, th->source, &ipv6h->daddr, @@ -979,9 +982,13 @@ static void tcp_v6_send_reset(const struct sock *sk, struct sk_buff *skb) oif = sk->sk_bound_dev_if; if (sk_fullsock(sk)) trace_tcp_send_reset(sk, skb); + } else { + if (net->ipv6.sysctl.flowlabel_reflect & 2) + label = ip6_flowlabel(ipv6h); } - tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, 0); + tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, + label); #ifdef CONFIG_TCP_MD5SIG out: