ipv4: IP_TOS and IP_TTL can be specified as ancillary data

This patch enables the IP_TTL and IP_TOS values passed from userspace to
be stored in the ipcm_cookie struct. Three fields are added to the struct:

- the TTL, expressed as __u8.
  The allowed values are in the [1-255].
  A value of 0 means that the TTL is not specified.

- the TOS, expressed as __s16.
  The allowed values are in the range [0,255].
  A value of -1 means that the TOS is not specified.

- the priority, expressed as a char and computed when
  handling the ancillary data.

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

2 files changed, 22 insertions, 1 deletions

diff --git a/include/net/ip.h b/include/net/ip.h
index c1f192b8cd0e..0135f3823e66 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -56,6 +56,9 @@ struct ipcm_cookie {
         int                     oif;
         struct ip_options_rcu   *opt;
         __u8                    tx_flags;
+        __u8                    ttl;
+        __s16                   tos;
+        char                    priority;
 };
 
 #define IPCB(skb) ((struct inet_skb_parm*)((skb)->cb))
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index d9c4f113d709..56e34457ac07 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -189,7 +189,7 @@ EXPORT_SYMBOL(ip_cmsg_recv);
 
 int ip_cmsg_send(struct net *net, struct msghdr *msg, struct ipcm_cookie *ipc)
 {
-        int err;
+        int err, val;
         struct cmsghdr *cmsg;
 
         for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) {
@@ -215,6 +215,24 @@ int ip_cmsg_send(struct net *net, struct msghdr *msg, struct ipcm_cookie *ipc)
                         ipc->addr = info->ipi_spec_dst.s_addr;
                         break;
                 }
+                case IP_TTL:
+                        if (cmsg->cmsg_len != CMSG_LEN(sizeof(int)))
+                                return -EINVAL;
+                        val = *(int *)CMSG_DATA(cmsg);
+                        if (val < 1 || val > 255)
+                                return -EINVAL;
+                        ipc->ttl = val;
+                        break;
+                case IP_TOS:
+                        if (cmsg->cmsg_len != CMSG_LEN(sizeof(int)))
+                                return -EINVAL;
+                        val = *(int *)CMSG_DATA(cmsg);
+                        if (val < 0 || val > 255)
+                                return -EINVAL;
+                        ipc->tos = val;
+                        ipc->priority = rt_tos2priority(ipc->tos);
+                        break;
+
                 default:
                         return -EINVAL;
                 }