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fix(capture): ignore known copy failure and fix iptables issue #903

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fix(capture): ignore known copy failure and fix iptables issue #903

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b95d2e4
ignore know copy failure and fix iptables issue
mainred Oct 29, 2024
f8cfb2d
Merge branch 'main' into capture/fix-iptables-error
mainred Oct 29, 2024
fac1200
return defined constant
mainred Oct 30, 2024
6ef95a3
Merge branch 'capture/fix-iptables-error' of github.com:mainred/retin…
mainred Oct 30, 2024
b173ff7
log iptables command error
mainred Oct 30, 2024
a012f53
return error when iptables comand is not available
mainred Jan 19, 2025
5a20113
Merge branch 'main' of github.com:microsoft/retina into capture/fix-i…
mainred Jan 19, 2025
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65 changes: 48 additions & 17 deletions pkg/capture/provider/network_capture_unix.go
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Original file line number Diff line number Diff line change
Expand Up @@ -188,15 +188,16 @@ func (ncp *NetworkCaptureProvider) CaptureNetworkPacket(filter string, duration,
}

type command struct {
name string
args []string
description string
name string
args []string
description string
ignoreFailure bool
}

func (ncp *NetworkCaptureProvider) CollectMetadata() error {
ncp.l.Info("Start to collect network metadata")

iptablesMode := obtainIptablesMode()
iptablesMode := obtainIptablesMode(ncp.l)
ncp.l.Info(fmt.Sprintf("Iptables mode %s is used", iptablesMode))
iptablesSaveCmdName := fmt.Sprintf("iptables-%s-save", iptablesMode)
iptablesCmdName := fmt.Sprintf("iptables-%s", iptablesMode)
Expand Down Expand Up @@ -282,9 +283,10 @@ func (ncp *NetworkCaptureProvider) CollectMetadata() error {
description: "networking stats",
},
{
name: "cp",
args: []string{"-r", "/proc/sys/net", filepath.Join(ncp.TmpCaptureDir, "proc-sys-net")},
description: "kernel networking configuration",
name: "cp",
args: []string{"-r", "/proc/sys/net", filepath.Join(ncp.TmpCaptureDir, "proc-sys-net")},
description: "kernel networking configuration",
ignoreFailure: true,
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Can we add a comment as to why this is optional? Also, maybe log this as a warn so that user doesn't go looking for this information in the capture.

},
},
},
Expand Down Expand Up @@ -320,14 +322,15 @@ func (ncp *NetworkCaptureProvider) CollectMetadata() error {
}

// Write command stdout and stderr to output file
for _, cmd := range cmds {
for _, command := range metadata.commands {
cmd := exec.Command(command.name, command.args...)
if _, err := outfile.WriteString(fmt.Sprintf("%s\n\n", cmd.String())); err != nil {
ncp.l.Error("Failed to write string to file", zap.String("file", outfile.Name()), zap.Error(err))
}

cmd.Stdout = outfile
cmd.Stderr = outfile
if err := cmd.Run(); err != nil {
if err := cmd.Run(); err != nil && !command.ignoreFailure {
// Don't return for error to continue capturing following network metadata.
ncp.l.Error("Failed to execute command", zap.String("command", cmd.String()), zap.Error(err))
// Log the error in output file because this error does not stop capture job pod from finishing,
Expand All @@ -342,7 +345,7 @@ func (ncp *NetworkCaptureProvider) CollectMetadata() error {
cmd := exec.Command(command.name, command.args...)
// Errors will when copying kernel networking configuration for not all files under /proc/sys/net are
// readable, like '/proc/sys/net/ipv4/route/flush', which doesn't implement the read function.
if output, err := cmd.CombinedOutput(); err != nil {
if output, err := cmd.CombinedOutput(); err != nil && !command.ignoreFailure {
// Don't return for error to continue capturing following network metadata.
ncp.l.Error("Failed to execute command", zap.String("command", cmd.String()), zap.String("output", string(output)), zap.Error(err))
}
Expand All @@ -361,16 +364,44 @@ func (ncp *NetworkCaptureProvider) Cleanup() error {
return nil
}

func obtainIptablesMode() string {
type iptablesMode string

const (
legacyIptablesMode iptablesMode = "legacy"
nftIptablesMode iptablesMode = "nft"
)

func obtainIptablesMode(l *log.ZapLogger) iptablesMode {
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I think you should return unhandled errors along with mode.

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The ideas in my mind is the failed iptables rules does not break the whole capture.

// Since iptables v1.8, nf_tables are introduced as an improvement of legacy iptables, but provides the same user
// interface as legacy iptables through iptables-nft command.
// based on: https://github.com/kubernetes-sigs/iptables-wrappers/blob/97b01f43a8e8db07840fc4b95e833a37c0d36b12/iptables-wrapper-installer.sh
legacySaveOut, _ := exec.Command("iptables-legacy-save").CombinedOutput()

// when both iptables modes available, we choose the one with more rules.
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nftIptablesModeAvaiable := true
legacyIptablesModeAvaiable := true
legacySaveOut, err := exec.Command("iptables-legacy-save").CombinedOutput()
if err != nil && strings.Contains(err.Error(), "command not found") {
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legacyIptablesModeAvaiable = false
}

legacySaveLineNum := len(strings.Split(string(legacySaveOut), "\n"))
nftSaveOut, _ := exec.Command("iptables-nft-save").CombinedOutput()
nftSaveLineNum := len(strings.Split(string(nftSaveOut), "\n"))
if legacySaveLineNum > nftSaveLineNum {
return "legacy"
nftSaveOut, err := exec.Command("iptables-nft-save").CombinedOutput()
if err != nil && strings.Contains(err.Error(), "command not found") {
nftIptablesModeAvaiable = false
}

if nftIptablesModeAvaiable && legacyIptablesModeAvaiable {
nftSaveLineNum := len(strings.Split(string(nftSaveOut), "\n"))
if legacySaveLineNum > nftSaveLineNum {
return legacyIptablesMode
}
return "nft"
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}

// when only one iptables mode available, we choose the available one when the other one is not available.
// when both iptables modes are not available, we choose the nft mode and let the iptables command fail.
if !nftIptablesModeAvaiable {
return legacyIptablesMode
}
return "nft"
return nftIptablesMode
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I want to highlight this again - we are returning nftIptablesMode even if we know that is not available. This assumes the behavior of the caller and shouldn't be done. We should return error if no mode is available and let the caller handle the error.

}
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