Re: [PATCH net-next 4/8] udp: never accept GSO_FRAGLIST packets

Currently the UDP protocol delivers GSO_FRAGLIST packets to
the sockets without the expected segmentation.

This change addresses the issue introducing and maintaining
a per socket bitmask of GSO types requiring segmentation.
Enabling GSO removes SKB_GSO_UDP_L4 from such mask, while
GSO_FRAGLIST packets are never accepted

Note: this also updates the 'unused' field size to really
fit the otherwise existing hole. It's size become incorrect
after commit bec1f6f69736 ("udp: generate gso with UDP_SEGMENT").

Fixes: 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 include/linux/udp.h | 10 ++++++----
 net/ipv4/udp.c      | 12 +++++++++++-
 2 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/include/linux/udp.h b/include/linux/udp.h
index aa84597bdc33c..6da342f15f351 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h

@@ -51,7 +51,7 @@ struct udp_sock {
                                           * different encapsulation layer set
                                           * this
                                           */
-                        gro_enabled:1; /* Can accept GRO packets */
+                        gro_enabled:1; /* Request GRO aggregation */

        /*
         * Following member retains the information to create a UDP header
         * when the socket is uncorked.

@@ -68,7 +68,10 @@ struct udp_sock {
 #define UDPLITE_SEND_CC  0x2           /* set via udplite setsockopt         */
 #define UDPLITE_RECV_CC  0x4           /* set via udplite setsocktopt        */
        __u8             pcflag;        /* marks socket as UDP-Lite if > 0    */
-       __u8             unused[3];
+       __u8             unused[1];
+       unsigned int     unexpected_gso;/* GSO types this socket can't accept,
+                                        * any of SKB_GSO_UDP_L4 or SKB_GSO_FRAGLIST
+                                        */

        /*
         * For encapsulation sockets.
         */

@@ -131,8 +134,7 @@ static inline void udp_cmsg_recv(struct msghdr *msg, struct sock *sk,

 static inline bool udp_unexpected_gso(struct sock *sk, struct sk_buff *skb)
 {
-       return !udp_sk(sk)->gro_enabled && skb_is_gso(skb) &&
-              skb_shinfo(skb)->gso_type & SKB_GSO_UDP_L4;
+       return skb_is_gso(skb) && skb_shinfo(skb)->gso_type & udp_sk(sk)->unexpected_gso;