[PATCH 21/28] ipv4: add ip_sock_set_mtu_discover

[Christoph Hellwig]

Add a helper to directly set the IP_MTU_DISCOVER sockopt from kernel
space without going through a fake uaccess.

Signed-off-by: Christoph Hellwig <h...@lst.de>
Reviewed-by: David Howells <dhowe...@redhat.com> [rxrpc bits]
---
 include/net/ip.h         |  1 +
 net/ipv4/ip_sockglue.c   | 11 +++++++++++
 net/rxrpc/local_object.c |  8 +-------
 net/rxrpc/output.c       | 14 +++++---------
 4 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index f063a491b9063..d3649c49dd333 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -766,6 +766,7 @@ static inline bool inetdev_valid_mtu(unsigned int mtu)
 }
 
 void ip_sock_set_freebind(struct sock *sk);
+int ip_sock_set_mtu_discover(struct sock *sk, int val);
 void ip_sock_set_recverr(struct sock *sk);
 void ip_sock_set_tos(struct sock *sk, int val);
 
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index aca6b81da9bae..aa115be11dcfb 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -597,6 +597,17 @@ void ip_sock_set_recverr(struct sock *sk)
 }
 EXPORT_SYMBOL(ip_sock_set_recverr);
 
+int ip_sock_set_mtu_discover(struct sock *sk, int val)
+{
+       if (val < IP_PMTUDISC_DONT || val > IP_PMTUDISC_OMIT)
+               return -EINVAL;
+       lock_sock(sk);
+       inet_sk(sk)->pmtudisc = val;
+       release_sock(sk);
+       return 0;
+}
+EXPORT_SYMBOL(ip_sock_set_mtu_discover);
+
 /*
  *     Socket option code for IP. This is the end of the line after any
  *     TCP,UDP etc options on an IP socket.
diff --git a/net/rxrpc/local_object.c b/net/rxrpc/local_object.c
index 4c0e8fe5ec1fb..6f4e6b4817cf2 100644
--- a/net/rxrpc/local_object.c
+++ b/net/rxrpc/local_object.c
@@ -174,13 +174,7 @@ static int rxrpc_open_socket(struct rxrpc_local *local, 
struct net *net)
                ip_sock_set_recverr(local->socket->sk);
 
                /* we want to set the don't fragment bit */
-               opt = IP_PMTUDISC_DO;
-               ret = kernel_setsockopt(local->socket, SOL_IP, IP_MTU_DISCOVER,
-                                       (char *) &opt, sizeof(opt));
-               if (ret < 0) {
-                       _debug("setsockopt failed");
-                       goto error;
-               }
+               ip_sock_set_mtu_discover(local->socket->sk, IP_PMTUDISC_DO);
 
                /* We want receive timestamps. */
                sock_enable_timestamps(local->socket->sk);
diff --git a/net/rxrpc/output.c b/net/rxrpc/output.c
index f8b632a5c6197..1ba43c3df4adb 100644
--- a/net/rxrpc/output.c
+++ b/net/rxrpc/output.c
@@ -321,7 +321,7 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, struct 
sk_buff *skb,
        struct kvec iov[2];
        rxrpc_serial_t serial;
        size_t len;
-       int ret, opt;
+       int ret;
 
        _enter(",{%d}", skb->len);
 
@@ -473,18 +473,14 @@ int rxrpc_send_data_packet(struct rxrpc_call *call, 
struct sk_buff *skb,
        switch (conn->params.local->srx.transport.family) {
        case AF_INET6:
        case AF_INET:
-               opt = IP_PMTUDISC_DONT;
-               kernel_setsockopt(conn->params.local->socket,
-                                 SOL_IP, IP_MTU_DISCOVER,
-                                 (char *)&opt, sizeof(opt));
+               ip_sock_set_mtu_discover(conn->params.local->socket->sk,
+                               IP_PMTUDISC_DONT);
                ret = kernel_sendmsg(conn->params.local->socket, &msg,
                                     iov, 2, len);
                conn->params.peer->last_tx_at = ktime_get_seconds();
 
-               opt = IP_PMTUDISC_DO;
-               kernel_setsockopt(conn->params.local->socket,
-                                 SOL_IP, IP_MTU_DISCOVER,
-                                 (char *)&opt, sizeof(opt));
+               ip_sock_set_mtu_discover(conn->params.local->socket->sk,
+                               IP_PMTUDISC_DO);
                break;
 
        default:
-- 
2.26.2