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conn: store IP_PKTINFO cmsg in StdNetendpoint src

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Replace the src storage inside StdNetEndpoint with a copy of the raw
control message buffer, to reduce allocation and perform less work on a
per-packet basis.

Signed-off-by: James Tucker <james@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
James Tucker
2023-04-18 22:29:55 -07:00
committed by Jason A. Donenfeld
parent b7cd547315
commit 25eb973e00
4 changed files with 128 additions and 98 deletions
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105
conn/sticky_linux.go
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@@ -14,6 +14,37 @@ import (
"golang.org/x/sys/unix"
)
func (e *StdNetEndpoint) SrcIP() netip.Addr {
switch len(e.src) {
case unix.CmsgSpace(unix.SizeofInet4Pktinfo):
info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&e.src[unix.CmsgLen(0)]))
return netip.AddrFrom4(info.Spec_dst)
case unix.CmsgSpace(unix.SizeofInet6Pktinfo):
info := (*unix.Inet6Pktinfo)(unsafe.Pointer(&e.src[unix.CmsgLen(0)]))
// TODO: set zone. in order to do so we need to check if the address is
// link local, and if it is perform a syscall to turn the ifindex into a
// zone string because netip uses string zones.
return netip.AddrFrom16(info.Addr)
}
return netip.Addr{}
}
func (e *StdNetEndpoint) SrcIfidx() int32 {
switch len(e.src) {
case unix.CmsgSpace(unix.SizeofInet4Pktinfo):
info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&e.src[unix.CmsgLen(0)]))
return info.Ifindex
case unix.CmsgSpace(unix.SizeofInet6Pktinfo):
info := (*unix.Inet6Pktinfo)(unsafe.Pointer(&e.src[unix.CmsgLen(0)]))
return int32(info.Ifindex)
}
return 0
}
func (e *StdNetEndpoint) SrcToString() string {
return e.SrcIP().String()
}
// getSrcFromControl parses the control for PKTINFO and if found updates ep with
// the source information found.
func getSrcFromControl(control []byte, ep *StdNetEndpoint) {
@@ -35,81 +66,43 @@ func getSrcFromControl(control []byte, ep *StdNetEndpoint) {
if hdr.Level == unix.IPPROTO_IP &&
hdr.Type == unix.IP_PKTINFO {
info := pktInfoFromBuf[unix.Inet4Pktinfo](data)
ep.src.Addr = netip.AddrFrom4(info.Spec_dst)
ep.src.ifidx = info.Ifindex
if ep.src == nil || cap(ep.src) < unix.CmsgSpace(unix.SizeofInet4Pktinfo) {
ep.src = make([]byte, 0, unix.CmsgSpace(unix.SizeofInet4Pktinfo))
}
ep.src = ep.src[:unix.CmsgSpace(unix.SizeofInet4Pktinfo)]
hdrBuf := unsafe.Slice((*byte)(unsafe.Pointer(&hdr)), unix.SizeofCmsghdr)
copy(ep.src, hdrBuf)
copy(ep.src[unix.CmsgLen(0):], data)
return
}
if hdr.Level == unix.IPPROTO_IPV6 &&
hdr.Type == unix.IPV6_PKTINFO {
info := pktInfoFromBuf[unix.Inet6Pktinfo](data)
ep.src.Addr = netip.AddrFrom16(info.Addr)
ep.src.ifidx = int32(info.Ifindex)
if ep.src == nil || cap(ep.src) < unix.CmsgSpace(unix.SizeofInet6Pktinfo) {
ep.src = make([]byte, 0, unix.CmsgSpace(unix.SizeofInet6Pktinfo))
}
ep.src = ep.src[:unix.CmsgSpace(unix.SizeofInet6Pktinfo)]
hdrBuf := unsafe.Slice((*byte)(unsafe.Pointer(&hdr)), unix.SizeofCmsghdr)
copy(ep.src, hdrBuf)
copy(ep.src[unix.CmsgLen(0):], data)
return
}
}
}
// pktInfoFromBuf returns type T populated from the provided buf via copy(). It
// panics if buf is of insufficient size.
func pktInfoFromBuf[T unix.Inet4Pktinfo | unix.Inet6Pktinfo](buf []byte) (t T) {
size := int(unsafe.Sizeof(t))
if len(buf) < size {
panic("pktInfoFromBuf: buffer too small")
}
copy(unsafe.Slice((*byte)(unsafe.Pointer(&t)), size), buf)
return t
}
// setSrcControl sets an IP{V6}_PKTINFO in control based on the source address
// and source ifindex found in ep. control's len will be set to 0 in the event
// that ep is a default value.
func setSrcControl(control *[]byte, ep *StdNetEndpoint) {
*control = (*control)[:cap(*control)]
if len(*control) < int(unsafe.Sizeof(unix.Cmsghdr{})) {
*control = (*control)[:0]
if cap(*control) < len(ep.src) {
return
}
if ep.src.ifidx == 0 && !ep.SrcIP().IsValid() {
*control = (*control)[:0]
return
}
if len(*control) < srcControlSize {
*control = (*control)[:0]
return
}
hdr := (*unix.Cmsghdr)(unsafe.Pointer(&(*control)[0]))
if ep.SrcIP().Is4() {
hdr.Level = unix.IPPROTO_IP
hdr.Type = unix.IP_PKTINFO
hdr.SetLen(unix.CmsgLen(unix.SizeofInet4Pktinfo))
info := (*unix.Inet4Pktinfo)(unsafe.Pointer(&(*control)[unix.SizeofCmsghdr]))
info.Ifindex = ep.src.ifidx
if ep.SrcIP().IsValid() {
info.Spec_dst = ep.SrcIP().As4()
}
*control = (*control)[:unix.CmsgSpace(unix.SizeofInet4Pktinfo)]
} else {
hdr.Level = unix.IPPROTO_IPV6
hdr.Type = unix.IPV6_PKTINFO
hdr.SetLen(unix.CmsgLen(unix.SizeofInet6Pktinfo))
info := (*unix.Inet6Pktinfo)(unsafe.Pointer(&(*control)[unix.SizeofCmsghdr]))
info.Ifindex = uint32(ep.src.ifidx)
if ep.SrcIP().IsValid() {
info.Addr = ep.SrcIP().As16()
}
*control = (*control)[:unix.CmsgSpace(unix.SizeofInet6Pktinfo)]
}
*control = (*control)[:0]
*control = append(*control, ep.src...)
}
var srcControlSize = unix.CmsgSpace(unix.SizeofInet6Pktinfo)