[PATCH v2] Allow UDP cmsghdrs through io_uring

[Victor Stewart <v@nametag.social>]

This patch adds PROTO_CMSG_DATA_ONLY to inet_dgram_ops and inet6_dgram_ops so that UDP_SEGMENT (GSO) and UDP_GRO can be used through io_uring.

GSO and GRO are vital to bring QUIC servers on par with TCP throughputs, and together offer a higher
throughput gain than io_uring alone (rate of data transit
considering), thus io_uring is presently the lesser performance choice.

RE http://vger.kernel.org/lpc_net2018_talks/willemdebruijn-lpc2018-udpgso-paper-DRAFT-1.pdf,
GSO is about +~63% and GRO +~82%.

this patch closes that loophole. 

net/ipv4/af_inet.c  | 1 +
net/ipv6/af_inet6.c | 1 +
net/socket.c        | 8 +++++---
3 files changed, 7 insertions(+), 3 deletions(-)