From: "R. Parameswaran" parameswaran.r7@gmail.com
commit 113c3075931a334f899008f6c753abe70a3a9323 upstream.
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 Signed-off-by: Giuliano Procida gprocida@google.com --- include/linux/net.h | 3 +++ net/socket.c | 46 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+)
diff --git a/include/linux/net.h b/include/linux/net.h index c00b8d182226..a0c6c00ac166 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -291,6 +291,9 @@ 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 15bdba4211ad..1a2a7320554b 100644 --- a/net/socket.c +++ b/net/socket.c @@ -3304,3 +3304,49 @@ 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);