From fc99a7ebf0c24b6f7b3cfd6351436373ed54548b Mon Sep 17 00:00:00 2001 From: Bhasker Hariharan Date: Fri, 3 Apr 2020 18:34:48 -0700 Subject: Refactor software GSO code. Software GSO implementation currently has a complicated code path with implicit assumptions that all packets to WritePackets carry same Data and it does this to avoid allocations on the path etc. But this makes it hard to reuse the WritePackets API. This change breaks all such assumptions by introducing a new Vectorised View API ReadToVV which can be used to cleanly split a VV into multiple independent VVs. Further this change also makes packet buffers linkable to form an intrusive list. This allows us to get rid of the array of packet buffers that are passed in the WritePackets API call and replace it with a list of packet buffers. While this code does introduce some more allocations in the benchmarks it doesn't cause any degradation. Updates #231 PiperOrigin-RevId: 304731742 --- pkg/tcpip/link/fdbased/endpoint.go | 162 +++++++++++++++++-------------------- 1 file changed, 75 insertions(+), 87 deletions(-) (limited to 'pkg/tcpip/link/fdbased') diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go index 3b3b6909b..7198742b7 100644 --- a/pkg/tcpip/link/fdbased/endpoint.go +++ b/pkg/tcpip/link/fdbased/endpoint.go @@ -441,118 +441,106 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, protocol tcpip.Ne // WritePackets writes outbound packets to the file descriptor. If it is not // currently writable, the packet is dropped. -func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts []stack.PacketBuffer, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) { - var ethHdrBuf []byte - // hdr + data - iovLen := 2 - if e.hdrSize > 0 { - // Add ethernet header if needed. - ethHdrBuf = make([]byte, header.EthernetMinimumSize) - eth := header.Ethernet(ethHdrBuf) - ethHdr := &header.EthernetFields{ - DstAddr: r.RemoteLinkAddress, - Type: protocol, - } - - // Preserve the src address if it's set in the route. - if r.LocalLinkAddress != "" { - ethHdr.SrcAddr = r.LocalLinkAddress - } else { - ethHdr.SrcAddr = e.addr - } - eth.Encode(ethHdr) - iovLen++ - } +// +// NOTE: This API uses sendmmsg to batch packets. As a result the underlying FD +// picked to write the packet out has to be the same for all packets in the +// list. In other words all packets in the batch should belong to the same +// flow. +func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) { + n := pkts.Len() - n := len(pkts) - - views := pkts[0].Data.Views() - /* - * Each boundary in views can add one more iovec. - * - * payload | | | | - * ----------------------------- - * packets | | | | | | | - * ----------------------------- - * iovecs | | | | | | | | | - */ - iovec := make([]syscall.Iovec, n*iovLen+len(views)-1) mmsgHdrs := make([]rawfile.MMsgHdr, n) + i := 0 + for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() { + var ethHdrBuf []byte + iovLen := 0 + if e.hdrSize > 0 { + // Add ethernet header if needed. + ethHdrBuf = make([]byte, header.EthernetMinimumSize) + eth := header.Ethernet(ethHdrBuf) + ethHdr := &header.EthernetFields{ + DstAddr: r.RemoteLinkAddress, + Type: protocol, + } - iovecIdx := 0 - viewIdx := 0 - viewOff := 0 - off := 0 - nextOff := 0 - for i := range pkts { - // TODO(b/134618279): Different packets may have different data - // in the future. We should handle this. - if !viewsEqual(pkts[i].Data.Views(), views) { - panic("All packets in pkts should have the same Data.") + // Preserve the src address if it's set in the route. + if r.LocalLinkAddress != "" { + ethHdr.SrcAddr = r.LocalLinkAddress + } else { + ethHdr.SrcAddr = e.addr + } + eth.Encode(ethHdr) + iovLen++ } - prevIovecIdx := iovecIdx - mmsgHdr := &mmsgHdrs[i] - mmsgHdr.Msg.Iov = &iovec[iovecIdx] - packetSize := pkts[i].DataSize - hdr := &pkts[i].Header - - off = pkts[i].DataOffset - if off != nextOff { - // We stop in a different point last time. - size := packetSize - viewIdx = 0 - viewOff = 0 - for size > 0 { - if size >= len(views[viewIdx]) { - viewIdx++ - viewOff = 0 - size -= len(views[viewIdx]) - } else { - viewOff = size - size = 0 + var vnetHdrBuf []byte + vnetHdr := virtioNetHdr{} + if e.Capabilities()&stack.CapabilityHardwareGSO != 0 { + if gso != nil { + vnetHdr.hdrLen = uint16(pkt.Header.UsedLength()) + if gso.NeedsCsum { + vnetHdr.flags = _VIRTIO_NET_HDR_F_NEEDS_CSUM + vnetHdr.csumStart = header.EthernetMinimumSize + gso.L3HdrLen + vnetHdr.csumOffset = gso.CsumOffset + } + if gso.Type != stack.GSONone && uint16(pkt.Data.Size()) > gso.MSS { + switch gso.Type { + case stack.GSOTCPv4: + vnetHdr.gsoType = _VIRTIO_NET_HDR_GSO_TCPV4 + case stack.GSOTCPv6: + vnetHdr.gsoType = _VIRTIO_NET_HDR_GSO_TCPV6 + default: + panic(fmt.Sprintf("Unknown gso type: %v", gso.Type)) + } + vnetHdr.gsoSize = gso.MSS } } + vnetHdrBuf = vnetHdrToByteSlice(&vnetHdr) + iovLen++ } - nextOff = off + packetSize + iovecs := make([]syscall.Iovec, iovLen+1+len(pkt.Data.Views())) + mmsgHdr := &mmsgHdrs[i] + mmsgHdr.Msg.Iov = &iovecs[0] + iovecIdx := 0 + if vnetHdrBuf != nil { + v := &iovecs[iovecIdx] + v.Base = &vnetHdrBuf[0] + v.Len = uint64(len(vnetHdrBuf)) + iovecIdx++ + } if ethHdrBuf != nil { - v := &iovec[iovecIdx] + v := &iovecs[iovecIdx] v.Base = ðHdrBuf[0] v.Len = uint64(len(ethHdrBuf)) iovecIdx++ } - - v := &iovec[iovecIdx] + pktSize := uint64(0) + // Encode L3 Header + v := &iovecs[iovecIdx] + hdr := &pkt.Header hdrView := hdr.View() v.Base = &hdrView[0] v.Len = uint64(len(hdrView)) + pktSize += v.Len iovecIdx++ - for packetSize > 0 { - vec := &iovec[iovecIdx] + // Now encode the Transport Payload. + pktViews := pkt.Data.Views() + for i := range pktViews { + vec := &iovecs[iovecIdx] iovecIdx++ - - v := views[viewIdx] - vec.Base = &v[viewOff] - s := len(v) - viewOff - if s <= packetSize { - viewIdx++ - viewOff = 0 - } else { - s = packetSize - viewOff += s - } - vec.Len = uint64(s) - packetSize -= s + vec.Base = &pktViews[i][0] + vec.Len = uint64(len(pktViews[i])) + pktSize += vec.Len } - - mmsgHdr.Msg.Iovlen = uint64(iovecIdx - prevIovecIdx) + mmsgHdr.Msg.Iovlen = uint64(iovecIdx) + i++ } packets := 0 for packets < n { - fd := e.fds[pkts[packets].Hash%uint32(len(e.fds))] + fd := e.fds[pkts.Front().Hash%uint32(len(e.fds))] sent, err := rawfile.NonBlockingSendMMsg(fd, mmsgHdrs) if err != nil { return packets, err -- cgit v1.2.3