On Sun, 2018-10-21 at 16:06 -0400, Willem de Bruijn wrote:
> On Fri, Oct 19, 2018 at 10:30 AM Paolo Abeni <pab...@redhat.com> wrote:
> >
> > This is the RX counterpart of commit bec1f6f69736 ("udp: generate gso
> > with UDP_SEGMENT"). When UDP_GRO is enabled, such socket is also
> > eligible for GRO in the rx path: UDP segments directed to such socket
> > are assembled into a larger GSO_UDP_L4 packet.
> >
> > The core UDP GRO support is enabled with setsockopt(UDP_GRO).
> >
> > Initial benchmark numbers:
> >
> > Before:
> > udp rx: 1079 MB/s 769065 calls/s
> >
> > After:
> > udp rx: 1466 MB/s 24877 calls/s
> >
> >
> > This change introduces a side effect in respect to UDP tunnels:
> > after a UDP tunnel creation, now the kernel performs a lookup per ingress
> > UDP packet, while before such lookup happened only if the ingress packet
> > carried a valid internal header csum.
> >
> > v1 -> v2:
> > - use a new option to enable UDP GRO
> > - use static keys to protect the UDP GRO socket lookup
> >
> > Signed-off-by: Paolo Abeni <pab...@redhat.com>
> > ---
> > include/linux/udp.h | 3 +-
> > include/uapi/linux/udp.h | 1 +
> > net/ipv4/udp.c | 7 +++
> > net/ipv4/udp_offload.c | 109 +++++++++++++++++++++++++++++++--------
> > net/ipv6/udp_offload.c | 6 +--
> > 5 files changed, 98 insertions(+), 28 deletions(-)
> >
> > diff --git a/include/linux/udp.h b/include/linux/udp.h
> > index a4dafff407fb..f613b329852e 100644
> > --- a/include/linux/udp.h
> > +++ b/include/linux/udp.h
> > @@ -50,11 +50,12 @@ struct udp_sock {
> > __u8 encap_type; /* Is this an Encapsulation socket?
> > */
> > unsigned char no_check6_tx:1,/* Send zero UDP6 checksums on TX?
> > */
> > no_check6_rx:1,/* Allow zero UDP6 checksums on RX?
> > */
> > - encap_enabled:1; /* This socket enabled encap
> > + encap_enabled:1, /* This socket enabled encap
> > * processing; UDP tunnels and
> > * different encapsulation layer
> > set
> > * this
> > */
> > + gro_enabled:1; /* Can accept GRO packets */
> >
> > /*
> > * Following member retains the information to create a UDP header
> > * when the socket is uncorked.
> > diff --git a/include/uapi/linux/udp.h b/include/uapi/linux/udp.h
> > index 09502de447f5..30baccb6c9c4 100644
> > --- a/include/uapi/linux/udp.h
> > +++ b/include/uapi/linux/udp.h
> > @@ -33,6 +33,7 @@ struct udphdr {
> > #define UDP_NO_CHECK6_TX 101 /* Disable sending checksum for UDP6X */
> > #define UDP_NO_CHECK6_RX 102 /* Disable accpeting checksum for UDP6 */
> > #define UDP_SEGMENT 103 /* Set GSO segmentation size */
> > +#define UDP_GRO 104 /* This socket can receive UDP GRO
> > packets */
> >
> > /* UDP encapsulation types */
> > #define UDP_ENCAP_ESPINUDP_NON_IKE 1 /*
> > draft-ietf-ipsec-nat-t-ike-00/01 */
> > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> > index 9fcb5374e166..3c277378814f 100644
> > --- a/net/ipv4/udp.c
> > +++ b/net/ipv4/udp.c
> > @@ -115,6 +115,7 @@
> > #include "udp_impl.h"
> > #include <net/sock_reuseport.h>
> > #include <net/addrconf.h>
> > +#include <net/udp_tunnel.h>
> >
> > struct udp_table udp_table __read_mostly;
> > EXPORT_SYMBOL(udp_table);
> > @@ -2459,6 +2460,12 @@ int udp_lib_setsockopt(struct sock *sk, int level,
> > int optname,
> > up->gso_size = val;
> > break;
> >
> > + case UDP_GRO:
> > + if (valbool)
> > + udp_tunnel_encap_enable(sk->sk_socket);
> > + up->gro_enabled = valbool;
>
> The socket lock is not held here, so multiple updates to
> up->gro_enabled and the up->encap_enabled and the static branch can
> race. Syzkaller is adept at generating those.
Good catch. I was fooled by the current existing code. I think there
are potentially similar issues for UDP_ENCAP, UDPLITE_SEND_CSCOV, ...
Since the rx path don't take it anymore and we don't risk starving, I
think we should could/always acquire the socket lock on setsockopt,
wdyt?
> > +#define UDO_GRO_CNT_MAX 64
> > +static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
> > + struct sk_buff *skb)
> > +{
> > + struct udphdr *uh = udp_hdr(skb);
> > + struct sk_buff *pp = NULL;
> > + struct udphdr *uh2;
> > + struct sk_buff *p;
> > +
> > + /* requires non zero csum, for simmetry with GSO */
>
> symmetry
Thanks ;)
Paolo
