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tcp: reflect tos value received in SYN to the socket

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This commit adds a new TCP feature to reflect the tos value received in
SYN, and send it out on the SYN-ACK, and eventually set the tos value of
the established socket with this reflected tos value. This provides a
way to set the traffic class/QoS level for all traffic in the same
connection to be the same as the incoming SYN request. It could be
useful in data centers to provide equivalent QoS according to the
incoming request.
This feature is guarded by /proc/sys/net/ipv4/tcp_reflect_tos, and is by
default turned off.

Signed-off-by: Wei Wang <weiwan@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Wei Wang
2020-09-09 17:50:48 -07:00
committed by David S. Miller
parent de033b7d15
commit ac8f1710c1
4 changed files with 28 additions and 2 deletions
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10
net/ipv6/tcp_ipv6.c
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@@ -510,6 +510,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
struct flowi6 *fl6 = &fl->u.ip6;
struct sk_buff *skb;
int err = -ENOMEM;
u8 tclass;
/* First, grab a route. */
if (!dst && (dst = inet6_csk_route_req(sk, fl6, req,
@@ -528,9 +529,12 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
rcu_read_lock();
opt = ireq->ipv6_opt;
tclass = sock_net(sk)->ipv4.sysctl_tcp_reflect_tos ?
tcp_rsk(req)->syn_tos : np->tclass;
if (!opt)
opt = rcu_dereference(np->opt);
err = ip6_xmit(sk, skb, fl6, sk->sk_mark, opt, np->tclass,
err = ip6_xmit(sk, skb, fl6, sk->sk_mark, opt,
tclass & ~INET_ECN_MASK,
sk->sk_priority);
rcu_read_unlock();
err = net_xmit_eval(err);
@@ -1310,6 +1314,10 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
if (np->repflow)
newnp->flow_label = ip6_flowlabel(ipv6_hdr(skb));
/* Set ToS of the new socket based upon the value of incoming SYN. */
if (sock_net(sk)->ipv4.sysctl_tcp_reflect_tos)
newnp->tclass = tcp_rsk(req)->syn_tos & ~INET_ECN_MASK;
/* Clone native IPv6 options from listening socket (if any)
Yes, keeping reference count would be much more clever,