ipv4: processing ancillary IP_TOS or IP_TTL

If IP_TOS or IP_TTL are specified as ancillary data, then sendmsg() sends out
packets with the specified TTL or TOS overriding the socket values specified
with the traditional setsockopt().

The struct inet_cork stores the values of TOS, TTL and priority that are
passed through the struct ipcm_cookie. If there are user-specified TOS
(tos != -1) or TTL (ttl != 0) in the struct ipcm_cookie, these values are
used to override the per-socket values. In case of TOS also the priority
is changed accordingly.

Two helper functions get_rttos and get_rtconn_flags are defined to take
into account the presence of a user specified TOS value when computing
RT_TOS and RT_CONN_FLAGS.

Signed-off-by: Francesco Fusco <ffusco@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 10 insertions, 3 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index a04d872c54f9..7d8357bb2ba6 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1060,6 +1060,9 @@ static int ip_setup_cork(struct sock *sk, struct inet_cork *cork,
                          rt->dst.dev->mtu : dst_mtu(&rt->dst);
         cork->dst = &rt->dst;
         cork->length = 0;
+        cork->ttl = ipc->ttl;
+        cork->tos = ipc->tos;
+        cork->priority = ipc->priority;
         cork->tx_flags = ipc->tx_flags;
 
         return 0;
@@ -1311,7 +1314,9 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
         if (cork->flags & IPCORK_OPT)
                 opt = cork->opt;
 
-        if (rt->rt_type == RTN_MULTICAST)
+        if (cork->ttl != 0)
+                ttl = cork->ttl;
+        else if (rt->rt_type == RTN_MULTICAST)
                 ttl = inet->mc_ttl;
         else
                 ttl = ip_select_ttl(inet, &rt->dst);
@@ -1319,7 +1324,7 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
         iph = ip_hdr(skb);
         iph->version = 4;
         iph->ihl = 5;
-        iph->tos = inet->tos;
+        iph->tos = (cork->tos != -1) ? cork->tos : inet->tos;
         iph->frag_off = df;
         iph->ttl = ttl;
         iph->protocol = sk->sk_protocol;
@@ -1331,7 +1336,7 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
                 ip_options_build(skb, opt, cork->addr, rt, 0);
         }
 
-        skb->priority = sk->sk_priority;
+        skb->priority = (cork->tos != -1) ? cork->priority: sk->sk_priority;
         skb->mark = sk->sk_mark;
         /*
          * Steal rt from cork.dst to avoid a pair of atomic_inc/atomic_dec
@@ -1481,6 +1486,8 @@ void ip_send_unicast_reply(struct net *net, struct sk_buff *skb, __be32 daddr,
         ipc.addr = daddr;
         ipc.opt = NULL;
         ipc.tx_flags = 0;
+        ipc.ttl = 0;
+        ipc.tos = -1;
 
         if (replyopts.opt.opt.optlen) {
                 ipc.opt = &replyopts.opt;