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net/netstat: add nil checks to Windows OSMetadata implementation

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The API documentation does claim to output empty strings under certain
conditions, but we're sometimes seeing nil pointers in the wild, not empty
strings.

Fixes https://github.com/tailscale/corp/issues/8878

Signed-off-by: Aaron Klotz <aaron@tailscale.com>
This commit is contained in:
Aaron Klotz 2023-01-27 09:31:00 -07:00
parent 8c03a31d10
commit 4a869048bf
1 changed files with 7 additions and 0 deletions
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7
net/netstat/netstat_windows.go
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@ -224,6 +224,7 @@ type moduleInfoConstraint interface {
_MIB_TCPROW_OWNER_MODULE | _MIB_TCP6ROW_OWNER_MODULE
}
// moduleInfo may return "", nil indicating a successful call but with empty data
func moduleInfo[entryType moduleInfoConstraint](entry *entryType, proc *windows.LazyProc) (string, error) {
var buf []byte
var desiredLen uint32
@ -249,6 +250,12 @@ func moduleInfo[entryType moduleInfoConstraint](entry *entryType, proc *windows.
}
basicInfo := (*_TCPIP_OWNER_MODULE_BASIC_INFO)(addr)
// GetOwnerModuleFromTcp*Entry is apparently using nil as an empty result
// under certain circumstances, so we check all the things.
if basicInfo == nil || basicInfo.moduleName == nil {
return "", nil
}
return windows.UTF16PtrToString(basicInfo.moduleName), nil
}