Parse /proc/net/protocols (#347)

This patch adds support for extracting system socket metrics found only in /proc/net/protocols. The most interesting metrics found here are per-protocol socket counts along with the total memory in pages used by each. For TCP connections this data can be used to tune/monitor a system against the thresholds set in net.ipv4.tcp_mem. This file also exposes a pressure metric which indicates whether or not a protocol like TCP has entered memory pressure, which again is useful in troubleshooting things like memory pressure induced packet drops on loopback.

Some additional albeit less interesting metrics that come out of this file include the size of each protocol's struct, and the maximum header size the kernel is willing to allocate.

The additional columns enumerate capabilities per-protocol and are encoded as bools.

Signed-off-by: Juan Bran <juan.bran@verizondigitalmedia.com>

fixtures.ttar

@@ -2129,6 +2129,24 @@ Lines: 6
        4    1FB3C        0          1282A8F                0
 Mode: 644
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+Path: fixtures/proc/net/protocols
+Lines: 14
+protocol  size sockets  memory press maxhdr  slab module     cl co di ac io in de sh ss gs se re sp bi br ha uh gp em
+PACKET    1344      2      -1   NI       0   no   kernel      n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n
+PINGv6    1112      0      -1   NI       0   yes  kernel      y  y  y  n  n  y  n  n  y  y  y  y  n  y  y  y  y  y  n
+RAWv6     1112      1      -1   NI       0   yes  kernel      y  y  y  n  y  y  y  n  y  y  y  y  n  y  y  y  y  n  n
+UDPLITEv6 1216      0      57   NI       0   yes  kernel      y  y  y  n  y  y  y  n  y  y  y  y  n  n  n  y  y  y  n
+UDPv6     1216     10      57   NI       0   yes  kernel      y  y  y  n  y  y  y  n  y  y  y  y  n  n  n  y  y  y  n
+TCPv6     2144   1937  1225378   no     320   yes  kernel      y  y  y  y  y  y  y  y  y  y  y  y  y  n  y  y  y  y  y
+UNIX      1024    120      -1   NI       0   yes  kernel      n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n
+UDP-Lite  1024      0      57   NI       0   yes  kernel      y  y  y  n  y  y  y  n  y  y  y  y  y  n  n  y  y  y  n
+PING       904      0      -1   NI       0   yes  kernel      y  y  y  n  n  y  n  n  y  y  y  y  n  y  y  y  y  y  n
+RAW        912      0      -1   NI       0   yes  kernel      y  y  y  n  y  y  y  n  y  y  y  y  n  y  y  y  y  n  n
+UDP       1024     73      57   NI       0   yes  kernel      y  y  y  n  y  y  y  n  y  y  y  y  y  n  n  y  y  y  n
+TCP       1984  93064  1225378   yes     320   yes  kernel      y  y  y  y  y  y  y  y  y  y  y  y  y  n  y  y  y  y  y
+NETLINK   1040     16      -1   NI       0   no   kernel      n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n  n
+Mode: 444
+# ttar - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 Directory: fixtures/proc/net/rpc
 Mode: 755
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net_protocols.go

@@ -0,0 +1,180 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package procfs
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/prometheus/procfs/internal/util"
+)
+
+// NetProtocolStats stores the contents from /proc/net/protocols
+type NetProtocolStats map[string]NetProtocolStatLine
+
+// NetProtocolStatLine contains a single line parsed from /proc/net/protocols. We
+// only care about the first six columns as the rest are not likely to change
+// and only serve to provide a set of capabilities for each protocol.
+type NetProtocolStatLine struct {
+	Name         string // 0 The name of the protocol
+	Size         uint64 // 1 The size, in bytes, of a given protocol structure. e.g. sizeof(struct tcp_sock) or sizeof(struct unix_sock)
+	Sockets      int64  // 2 Number of sockets in use by this protocol
+	Memory       int64  // 3 Number of 4KB pages allocated by all sockets of this protocol
+	Pressure     int    // 4 This is either yes, no, or NI (not implemented). For the sake of simplicity we treat NI as not experiencing memory pressure.
+	MaxHeader    uint64 // 5 Protocol specific max header size
+	Slab         bool   // 6 Indicates whether or not memory is allocated from the SLAB
+	ModuleName   string // 7 The name of the module that implemented this protocol or "kernel" if not from a module
+	Capabilities NetProtocolCapabilities
+}
+
+// NetProtocolCapabilities contains a list of capabilities for each protocol
+type NetProtocolCapabilities struct {
+	Close               bool // 8
+	Connect             bool // 9
+	Disconnect          bool // 10
+	Accept              bool // 11
+	IoCtl               bool // 12
+	Init                bool // 13
+	Destroy             bool // 14
+	Shutdown            bool // 15
+	SetSockOpt          bool // 16
+	GetSockOpt          bool // 17
+	SendMsg             bool // 18
+	RecvMsg             bool // 19
+	SendPage            bool // 20
+	Bind                bool // 21
+	BacklogRcv          bool // 22
+	Hash                bool // 23
+	UnHash              bool // 24
+	GetPort             bool // 25
+	EnterMemoryPressure bool // 26
+}
+
+// NetProtocols reads stats from /proc/net/protocols and returns a map of
+// PortocolStatLine entries. As of this writing no official Linux Documentation
+// exists, however the source is fairly self-explanatory and the format seems
+// stable since its introduction in 2.6.12-rc2
+// Linux 2.6.12-rc2 - https://elixir.bootlin.com/linux/v2.6.12-rc2/source/net/core/sock.c#L1452
+// Linux 5.10 - https://elixir.bootlin.com/linux/v5.10.4/source/net/core/sock.c#L3586
+func (fs FS) NetProtocols() (NetProtocolStats, error) {
+	data, err := util.ReadFileNoStat(fs.proc.Path("net/protocols"))
+	if err != nil {
+		return NetProtocolStats{}, err
+	}
+	return parseNetProtocols(bufio.NewScanner(bytes.NewReader(data)))
+}
+
+func parseNetProtocols(s *bufio.Scanner) (NetProtocolStats, error) {
+	nps := NetProtocolStats{}
+
+	// Skip the header line
+	s.Scan()
+
+	for s.Scan() {
+		line, err := nps.parseLine(s.Text())
+		if err != nil {
+			return NetProtocolStats{}, err
+		}
+
+		nps[line.Name] = *line
+	}
+	return nps, nil
+}
+
+func (ps NetProtocolStats) parseLine(rawLine string) (*NetProtocolStatLine, error) {
+	line := &NetProtocolStatLine{Capabilities: NetProtocolCapabilities{}}
+	var err error
+	const enabled = "yes"
+	const disabled = "no"
+
+	fields := strings.Fields(rawLine)
+	line.Name = fields[0]
+	line.Size, err = strconv.ParseUint(fields[1], 10, 64)
+	if err != nil {
+		return nil, err
+	}
+	line.Sockets, err = strconv.ParseInt(fields[2], 10, 64)
+	if err != nil {
+		return nil, err
+	}
+	line.Memory, err = strconv.ParseInt(fields[3], 10, 64)
+	if err != nil {
+		return nil, err
+	}
+	if fields[4] == enabled {
+		line.Pressure = 1
+	} else if fields[4] == disabled {
+		line.Pressure = 0
+	} else {
+		line.Pressure = -1
+	}
+	line.MaxHeader, err = strconv.ParseUint(fields[5], 10, 64)
+	if err != nil {
+		return nil, err
+	}
+	if fields[6] == enabled {
+		line.Slab = true
+	} else if fields[6] == disabled {
+		line.Slab = false
+	} else {
+		return nil, fmt.Errorf("unable to parse capability for protocol: %s", line.Name)
+	}
+	line.ModuleName = fields[7]
+
+	err = line.Capabilities.parseCapabilities(fields[8:])
+	if err != nil {
+		return nil, err
+	}
+
+	return line, nil
+}
+
+func (pc *NetProtocolCapabilities) parseCapabilities(capabilities []string) error {
+	// The capabilities are all bools so we can loop over to map them
+	capabilityFields := [...]*bool{
+		&pc.Close,
+		&pc.Connect,
+		&pc.Disconnect,
+		&pc.Accept,
+		&pc.IoCtl,
+		&pc.Init,
+		&pc.Destroy,
+		&pc.Shutdown,
+		&pc.SetSockOpt,
+		&pc.GetSockOpt,
+		&pc.SendMsg,
+		&pc.RecvMsg,
+		&pc.SendPage,
+		&pc.Bind,
+		&pc.BacklogRcv,
+		&pc.Hash,
+		&pc.UnHash,
+		&pc.GetPort,
+		&pc.EnterMemoryPressure,
+	}
+
+	for i := 0; i < len(capabilities); i++ {
+		if capabilities[i] == "y" {
+			*capabilityFields[i] = true
+		} else if capabilities[i] == "n" {
+			*capabilityFields[i] = false
+		} else {
+			return fmt.Errorf("unable to parse capability block for protocol: position %d", i)
+		}
+	}
+	return nil
+}

net_protocols_test.go

@@ -0,0 +1,83 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package procfs
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestParseCapabilities(t *testing.T) {
+	rawStr := "y  y  y  y  y  y  y  y  y  y  y  y  y  n  y  y  y  y  y\n"
+	have := NetProtocolCapabilities{}
+	err := have.parseCapabilities(strings.Fields(rawStr))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := NetProtocolCapabilities{true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, true, true, true, true}
+	if want != have {
+		t.Errorf("want %+v\nhave %+v\n", want, have)
+	}
+}
+
+func TestProtocolsParseLine(t *testing.T) {
+	rawStr := "TCP       1984  93064  1225378   no     320   yes  kernel      y  y  y  y  y  y  y  y  y  y  y  y  y  n  y  y  y  y  y\n"
+	protocols := NetProtocolStats{}
+	have, err := protocols.parseLine(rawStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	want := NetProtocolStatLine{"TCP", 1984, 93064, 1225378, 0, 320, true, "kernel", NetProtocolCapabilities{true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, true, true, true, true}}
+	if want != *have {
+		t.Errorf("want %+v\nhave %+v\n", want, have)
+	}
+}
+
+func TestProtocolsParseProtocols(t *testing.T) {
+	fs, err := NewFS(procTestFixtures)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	protocolStats, err := fs.NetProtocols()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	lines := map[string]NetProtocolStatLine{
+		"PACKET":    {"PACKET", 1344, 2, -1, -1, 0, false, "kernel", NetProtocolCapabilities{false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false}},
+		"PINGv6":    {"PINGv6", 1112, 0, -1, -1, 0, true, "kernel", NetProtocolCapabilities{true, true, true, false, false, true, false, false, true, true, true, true, false, true, true, true, true, true, false}},
+		"RAWv6":     {"RAWv6", 1112, 1, -1, -1, 0, true, "kernel", NetProtocolCapabilities{true, true, true, false, true, true, true, false, true, true, true, true, false, true, true, true, true, false, false}},
+		"UDPLITEv6": {"UDPLITEv6", 1216, 0, 57, -1, 0, true, "kernel", NetProtocolCapabilities{true, true, true, false, true, true, true, false, true, true, true, true, false, false, false, true, true, true, false}},
+		"UDPv6":     {"UDPv6", 1216, 10, 57, -1, 0, true, "kernel", NetProtocolCapabilities{true, true, true, false, true, true, true, false, true, true, true, true, false, false, false, true, true, true, false}},
+		"TCPv6":     {"TCPv6", 2144, 1937, 1225378, 0, 320, true, "kernel", NetProtocolCapabilities{true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, true, true, true, true}},
+		"UNIX":      {"UNIX", 1024, 120, -1, -1, 0, true, "kernel", NetProtocolCapabilities{false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false}},
+		"UDP-Lite":  {"UDP-Lite", 1024, 0, 57, -1, 0, true, "kernel", NetProtocolCapabilities{true, true, true, false, true, true, true, false, true, true, true, true, true, false, false, true, true, true, false}},
+		"PING":      {"PING", 904, 0, -1, -1, 0, true, "kernel", NetProtocolCapabilities{true, true, true, false, false, true, false, false, true, true, true, true, false, true, true, true, true, true, false}},
+		"RAW":       {"RAW", 912, 0, -1, -1, 0, true, "kernel", NetProtocolCapabilities{true, true, true, false, true, true, true, false, true, true, true, true, false, true, true, true, true, false, false}},
+		"UDP":       {"UDP", 1024, 73, 57, -1, 0, true, "kernel", NetProtocolCapabilities{true, true, true, false, true, true, true, false, true, true, true, true, true, false, false, true, true, true, false}},
+		"TCP":       {"TCP", 1984, 93064, 1225378, 1, 320, true, "kernel", NetProtocolCapabilities{true, true, true, true, true, true, true, true, true, true, true, true, true, false, true, true, true, true, true}},
+		"NETLINK":   {"NETLINK", 1040, 16, -1, -1, 0, false, "kernel", NetProtocolCapabilities{false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false, false}},
+	}
+
+	if want, have := len(lines), len(protocolStats); want != have {
+		t.Errorf("want %d parsed net/protocols lines, have %d", want, have)
+	}
+	for _, line := range protocolStats {
+		if want, have := lines[line.Name], line; want != have {
+			t.Errorf("%s: want %v, have %v", line.Name, want, have)
+		}
+	}
+}