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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 22b6722bfa ("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 <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2019-06-05 07:55:09 -07:00 committed by David S. Miller
parent e736bf72af
commit 323a53c412
4 changed files with 29 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
Documentation/networking/ip-sysctl.txt
View File

@ -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.

2
net/ipv6/af_inet6.c
View File

@ -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

3
net/ipv6/sysctl_net_ipv6.c
View File

@ -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",

13
net/ipv6/tcp_ipv6.c
View File

@ -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: