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.
Signed-off-by: R. Parameswaran <rpara...@brocade.com>
---
include/linux/net.h | 3 +++
net/socket.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 47 insertions(+)
diff --git a/include/linux/net.h b/include/linux/net.h
index 0620f5e..a42fab2 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -298,6 +298,9 @@ int kernel_sendpage(struct socket *sock, struct page *page,
int offset,
int kernel_sock_ioctl(struct socket *sock, int cmd, unsigned long arg);
int kernel_sock_shutdown(struct socket *sock, enum sock_shutdown_cmd how);
+/* Following routine returns the IP overhead imposed by a socket. */
+u32 kernel_sock_ip_overhead(struct sock *sk);
+
#define MODULE_ALIAS_NETPROTO(proto) \
MODULE_ALIAS("net-pf-" __stringify(proto))
diff --git a/net/socket.c b/net/socket.c
index e034fe4..69598e1 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -3345,3 +3345,47 @@ 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 ipv6_pinfo *np;
+ struct ip_options_rcu *opt;
+ struct ipv6_txoptions *optv6 = NULL;
+ u32 overhead = 0;
+ bool owned_by_user;
+
+ 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);
--
2.1.4
