| Message ID | 20230301211146.1974507-1-willemdebruijn.kernel@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [manpages,1/2] udp.7: add UDP_SEGMENT | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
Hi Willem, On 3/1/23 22:11, Willem de Bruijn wrote: > From: Willem de Bruijn <willemb@google.com> > > UDP_SEGMENT was added in commit bec1f6f69736 > ("udp: generate gso with UDP_SEGMENT") > > $ git describe --contains bec1f6f69736 > linux/v4.18-rc1~114^2~377^2~8 > > Kernel source has example code in tools/testing/selftests/net/udpgso* > > Per https://www.kernel.org/doc/man-pages/patches.html, > "Describe how you obtained the information in your patch": > I am the author of the above commit and follow-ons. > > Signed-off-by: Willem de Bruijn <willemb@google.com> > --- > man7/udp.7 | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+) > > diff --git a/man7/udp.7 b/man7/udp.7 > index 5822bc551fdf..ec16306df605 100644 > --- a/man7/udp.7 > +++ b/man7/udp.7 > @@ -204,6 +204,31 @@ portable. > .\" UDP_ENCAP_ESPINUDP draft-ietf-ipsec-udp-encaps-06 > .\" UDP_ENCAP_L2TPINUDP rfc2661 > .\" FIXME Document UDP_NO_CHECK6_TX and UDP_NO_CHECK6_RX, added in Linux 3.16 > +.TP > +.BR UDP_SEGMENT " (since Linux 4.18)" > +Enables UDP segmentation offload. > +Segmentation offload reduces > +.BR send(2) > +cost by transferring multiple datagrams worth of data as a single > +large packet through the kernel transmit path, even when that Please use semantic newlines. See man-pages(7): Use semantic newlines In the source of a manual page, new sentences should be started on new lines, long sentences should be split into lines at clause breaks (commas, semicolons, colons, and so on), and long clauses should be split at phrase boundaries. This convention, sometimes known as "semantic newlines", makes it easier to see the effect of patches, which often operate at the level of in‐ dividual sentences, clauses, or phrases. > +exceeds MTU. > +As late as possible, the large packet is split by segment size into a > +series of datagrams. > +This segmentation offload step is deferred to hardware if supported, > +else performed in software. > +This option takes a value between 0 and USHRT_MAX that sets the > +segment size: the size of datagram payload, excluding the UDP header. > +The segment size must be chosen such that at most 64 datagrams are > +sent in a single call and that the datagrams after segmentation meet > +the same MTU rules that apply to datagrams sent without this option. > +Segmentation offload depends on checksum offload, as datagram > +checksums are computed after segmentation. > +The option may also be set for individual > +.BR sendmsg(2) There should be a space between the bold part and the roman part: .BR foo (2) Otherwise, it all gets printed in bold. Cheers, Alex > +calls by passing it as a > +.BR cmsg(7). > +A value of zero disables the feature. > +This option should not be used in code intended to be portable. > .SS Ioctls > These ioctls can be accessed using > .BR ioctl (2).
On Wed, Mar 1, 2023 at 4:35 PM Alejandro Colomar <alx.manpages@gmail.com> wrote: > > Hi Willem, > > On 3/1/23 22:11, Willem de Bruijn wrote: > > From: Willem de Bruijn <willemb@google.com> > > > > UDP_SEGMENT was added in commit bec1f6f69736 > > ("udp: generate gso with UDP_SEGMENT") > > > > $ git describe --contains bec1f6f69736 > > linux/v4.18-rc1~114^2~377^2~8 > > > > Kernel source has example code in tools/testing/selftests/net/udpgso* > > > > Per https://www.kernel.org/doc/man-pages/patches.html, > > "Describe how you obtained the information in your patch": > > I am the author of the above commit and follow-ons. > > > > Signed-off-by: Willem de Bruijn <willemb@google.com> > > --- > > man7/udp.7 | 25 +++++++++++++++++++++++++ > > 1 file changed, 25 insertions(+) > > > > diff --git a/man7/udp.7 b/man7/udp.7 > > index 5822bc551fdf..ec16306df605 100644 > > --- a/man7/udp.7 > > +++ b/man7/udp.7 > > @@ -204,6 +204,31 @@ portable. > > .\" UDP_ENCAP_ESPINUDP draft-ietf-ipsec-udp-encaps-06 > > .\" UDP_ENCAP_L2TPINUDP rfc2661 > > .\" FIXME Document UDP_NO_CHECK6_TX and UDP_NO_CHECK6_RX, added in Linux 3.16 > > +.TP > > +.BR UDP_SEGMENT " (since Linux 4.18)" > > +Enables UDP segmentation offload. > > +Segmentation offload reduces > > +.BR send(2) > > +cost by transferring multiple datagrams worth of data as a single > > +large packet through the kernel transmit path, even when that > > Please use semantic newlines. See man-pages(7): > > Use semantic newlines > In the source of a manual page, new sentences should be started > on new lines, long sentences should be split into lines at > clause breaks (commas, semicolons, colons, and so on), and long > clauses should be split at phrase boundaries. This convention, > sometimes known as "semantic newlines", makes it easier to see > the effect of patches, which often operate at the level of in‐ > dividual sentences, clauses, or phrases. > > > > +exceeds MTU. > > +As late as possible, the large packet is split by segment size into a > > +series of datagrams. > > +This segmentation offload step is deferred to hardware if supported, > > +else performed in software. > > +This option takes a value between 0 and USHRT_MAX that sets the > > +segment size: the size of datagram payload, excluding the UDP header. > > +The segment size must be chosen such that at most 64 datagrams are > > +sent in a single call and that the datagrams after segmentation meet > > +the same MTU rules that apply to datagrams sent without this option. > > +Segmentation offload depends on checksum offload, as datagram > > +checksums are computed after segmentation. > > +The option may also be set for individual > > +.BR sendmsg(2) > > There should be a space between the bold part and the roman part: > > .BR foo (2) > > Otherwise, it all gets printed in bold. Thanks Alex. I'll leave this open for other comments for a bit, but will address both points in both patches in v2.
diff --git a/man7/udp.7 b/man7/udp.7 index 5822bc551fdf..ec16306df605 100644 --- a/man7/udp.7 +++ b/man7/udp.7 @@ -204,6 +204,31 @@ portable. .\" UDP_ENCAP_ESPINUDP draft-ietf-ipsec-udp-encaps-06 .\" UDP_ENCAP_L2TPINUDP rfc2661 .\" FIXME Document UDP_NO_CHECK6_TX and UDP_NO_CHECK6_RX, added in Linux 3.16 +.TP +.BR UDP_SEGMENT " (since Linux 4.18)" +Enables UDP segmentation offload. +Segmentation offload reduces +.BR send(2) +cost by transferring multiple datagrams worth of data as a single +large packet through the kernel transmit path, even when that +exceeds MTU. +As late as possible, the large packet is split by segment size into a +series of datagrams. +This segmentation offload step is deferred to hardware if supported, +else performed in software. +This option takes a value between 0 and USHRT_MAX that sets the +segment size: the size of datagram payload, excluding the UDP header. +The segment size must be chosen such that at most 64 datagrams are +sent in a single call and that the datagrams after segmentation meet +the same MTU rules that apply to datagrams sent without this option. +Segmentation offload depends on checksum offload, as datagram +checksums are computed after segmentation. +The option may also be set for individual +.BR sendmsg(2) +calls by passing it as a +.BR cmsg(7). +A value of zero disables the feature. +This option should not be used in code intended to be portable. .SS Ioctls These ioctls can be accessed using .BR ioctl (2).