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, 3 insertions, 1 deletions

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 74d2c95db57f..22462d947750 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -855,6 +855,8 @@ int udp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 
         ipc.opt = NULL;
         ipc.tx_flags = 0;
+        ipc.ttl = 0;
+        ipc.tos = -1;
 
         getfrag = is_udplite ? udplite_getfrag : ip_generic_getfrag;
 
@@ -938,7 +940,7 @@ int udp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
                 faddr = ipc.opt->opt.faddr;
                 connected = 0;
         }
-        tos = RT_TOS(inet->tos);
+        tos = get_rttos(&ipc, inet);
         if (sock_flag(sk, SOCK_LOCALROUTE) ||
             (msg->msg_flags & MSG_DONTROUTE) ||
             (ipc.opt && ipc.opt->opt.is_strictroute)) {