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authorR. Parameswaran <parameswaran.r7@gmail.com>2017-04-05 16:50:35 -0700
committerDavid S. Miller <davem@davemloft.net>2017-04-06 13:43:31 -0700
commit113c3075931a334f899008f6c753abe70a3a9323 (patch)
treea0f7e868672699b451a5053824eea0df16ce07cc /net/socket.c
parent129858fa0b1ab3072155718b74bf91e440c2d73f (diff)
downloadlwn-113c3075931a334f899008f6c753abe70a3a9323.tar.gz
lwn-113c3075931a334f899008f6c753abe70a3a9323.zip
New kernel function to get IP overhead on a socket.
A new function, kernel_sock_ip_overhead(), is provided to calculate the cumulative overhead imposed by the IP Header and IP options, if any, on a socket's payload. The new function returns an overhead of zero for sockets that do not belong to the IPv4 or IPv6 address families. This is used in the L2TP code path to compute the total outer IP overhead on the L2TP tunnel socket when calculating the default MTU for Ethernet pseudowires. Signed-off-by: R. Parameswaran <rparames@brocade.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/socket.c')
-rw-r--r--net/socket.c46
1 files changed, 46 insertions, 0 deletions
diff --git a/net/socket.c b/net/socket.c
index 985ef06792d6..eea997036ada 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -3356,3 +3356,49 @@ int kernel_sock_shutdown(struct socket *sock, enum sock_shutdown_cmd how)
return sock->ops->shutdown(sock, how);
}
EXPORT_SYMBOL(kernel_sock_shutdown);
+
+/* This routine returns the IP overhead imposed by a socket i.e.
+ * the length of the underlying IP header, depending on whether
+ * this is an IPv4 or IPv6 socket and the length from IP options turned
+ * on at the socket.
+ */
+u32 kernel_sock_ip_overhead(struct sock *sk)
+{
+ struct inet_sock *inet;
+ struct ip_options_rcu *opt;
+ u32 overhead = 0;
+ bool owned_by_user;
+#if IS_ENABLED(CONFIG_IPV6)
+ struct ipv6_pinfo *np;
+ struct ipv6_txoptions *optv6 = NULL;
+#endif /* IS_ENABLED(CONFIG_IPV6) */
+
+ if (!sk)
+ return overhead;
+
+ owned_by_user = sock_owned_by_user(sk);
+ switch (sk->sk_family) {
+ case AF_INET:
+ inet = inet_sk(sk);
+ overhead += sizeof(struct iphdr);
+ opt = rcu_dereference_protected(inet->inet_opt,
+ owned_by_user);
+ if (opt)
+ overhead += opt->opt.optlen;
+ return overhead;
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
+ np = inet6_sk(sk);
+ overhead += sizeof(struct ipv6hdr);
+ if (np)
+ optv6 = rcu_dereference_protected(np->opt,
+ owned_by_user);
+ if (optv6)
+ overhead += (optv6->opt_flen + optv6->opt_nflen);
+ return overhead;
+#endif /* IS_ENABLED(CONFIG_IPV6) */
+ default: /* Returns 0 overhead if the socket is not ipv4 or ipv6 */
+ return overhead;
+ }
+}
+EXPORT_SYMBOL(kernel_sock_ip_overhead);