Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

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

Open
wants to merge 6 commits into
base: main
Choose a base branch
from
Open

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

Changes from all commits
Commits
Show all changes
6 commits
Select commit Hold shift + click to select a range
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
e028a85
Merge branch 'main' into capture/fix-iptables-error
mainred Nov 19, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
65 changes: 49 additions & 16 deletions pkg/capture/provider/network_capture_unix.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -191,15 +191,16 @@
}

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 @@ -285,9 +286,10 @@
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,
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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 @@ -323,14 +325,15 @@
}

// Write command stdout and stderr to output file
for _, cmd := range cmds {
for _, command := range metadata.commands {
cmd := exec.Command(command.name, command.args...)

Check failure on line 329 in pkg/capture/provider/network_capture_unix.go

View workflow job for this annotation

GitHub Actions / Lint (linux, arm64) 

G204: Subprocess launched with a potential tainted input or cmd arguments (gosec)

Check failure on line 329 in pkg/capture/provider/network_capture_unix.go

View workflow job for this annotation

GitHub Actions / Lint (linux, amd64) 

G204: Subprocess launched with a potential tainted input or cmd arguments (gosec)
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 @@ -345,7 +348,7 @@
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 @@ -364,16 +367,46 @@
return nil
}

func obtainIptablesMode() string {
type iptablesMode string

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

func obtainIptablesMode(logger *log.ZapLogger) iptablesMode {
// 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, because the other one normally outputs empty rules.
nftIptablesModeAvaiable := true
legacyIptablesModeAvaiable := true
legacySaveOut, err := exec.Command("iptables-legacy-save").CombinedOutput()
if err != nil {
nftIptablesModeAvaiable = false
logger.Error("Failed to run iptables-legacy-save", zap.Error(err))
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think we should make this more verbose. This error doesn't indicate the tool failed to collect capture; it just indicates the command may not be available.

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@anubhabMajumdar It doesn't even really indicate that since weird things can go wrong when exec'ing under a stressed-out system. If we want to definitively test whether the command exists or not, the correct way to do that is with exec.LookPath. We should preflight each of these invocations to rule out the command not existing first (which can be done without exec()ing too). Then if we hit this arm of the error, we know definitively that it was something unusual in the actual execution of the command (probably OOM or something).

Also, in general, if it's happy-path control flow that the command does not exist (which we could be certain of with exec.LookPath, we don't need to log the error (since it's not an error). Once we are sure that it's an unusual error, we should return the error from this func, wrapped with context about what we were trying to do when the error was produced.

}
legacySaveLineNum := len(strings.Split(string(legacySaveOut), "\n"))
nftSaveOut, _ := exec.Command("iptables-nft-save").CombinedOutput()

nftSaveOut, err := exec.Command("iptables-nft-save").CombinedOutput()
if err != nil {
nftIptablesModeAvaiable = false
logger.Error("Failed to run iptables-nft-save", zap.Error(err))
}
nftSaveLineNum := len(strings.Split(string(nftSaveOut), "\n"))
if legacySaveLineNum > nftSaveLineNum {
return "legacy"

if nftIptablesModeAvaiable && legacyIptablesModeAvaiable {
if legacySaveLineNum > nftSaveLineNum {
return legacyIptablesMode
}
return nftIptablesMode
}

// 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
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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.

}
Loading