net: implement IP_RECVTOS for IP_PKTOPTIONS

Currently, it is not easily possible to get TOS/DSCP value of packets from
an incoming TCP stream. The mechanism is there, IP_PKTOPTIONS getsockopt
with IP_RECVTOS set, the same way as incoming TTL can be queried. This is
not actually implemented for TOS, though.

This patch adds this functionality, both for IPv4 (IP_PKTOPTIONS) and IPv6
(IPV6_2292PKTOPTIONS). For IPv4, like in the IP_RECVTTL case, the value of
the TOS field is stored from the other party's ACK.

This is needed for proxies which require DSCP transparency. One such example
is at http://zph.bratcheda.org/.

Signed-off-by: Jiri Benc <jbenc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d16414cb3421..12c6ece67f39 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1282,6 +1282,7 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
                 newnp->opt         = NULL;
                 newnp->mcast_oif   = inet6_iif(skb);
                 newnp->mcast_hops  = ipv6_hdr(skb)->hop_limit;
+                newnp->rcv_tclass  = ipv6_tclass(ipv6_hdr(skb));
 
                 /*
                  * No need to charge this sock to the relevant IPv6 refcnt debug socks count
@@ -1360,6 +1361,7 @@ static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
         newnp->opt        = NULL;
         newnp->mcast_oif  = inet6_iif(skb);
         newnp->mcast_hops = ipv6_hdr(skb)->hop_limit;
+        newnp->rcv_tclass = ipv6_tclass(ipv6_hdr(skb));
 
         /* Clone native IPv6 options from listening socket (if any)
 
@@ -1562,6 +1564,8 @@ ipv6_pktoptions:
                         np->mcast_oif = inet6_iif(opt_skb);
                 if (np->rxopt.bits.rxhlim || np->rxopt.bits.rxohlim)
                         np->mcast_hops = ipv6_hdr(opt_skb)->hop_limit;
+                if (np->rxopt.bits.rxtclass)
+                        np->rcv_tclass = ipv6_tclass(ipv6_hdr(skb));
                 if (ipv6_opt_accepted(sk, opt_skb)) {
                         skb_set_owner_r(opt_skb, sk);
                         opt_skb = xchg(&np->pktoptions, opt_skb);