feat: calculate boot time correctly if the time jumps

smira · smira · commit 6f7d20b8223a · 2026-03-13T21:39:27.000+04:00
Instead of capturing boot time difference with `time.Now()` just once at
the beginning of streaming kmsg events, re-check the `time.Now()` while
processing each message.

This fixes issue with kmsg logs as seens e.g. from RPi: as it has not
RTC, it might streaming ksmg logs while time is back at zero (1970), but
as NTP catches up, the stream still reports dates in 1970, not accepting
the fact that the NTP caught up.

Signed-off-by: Andrey Smirnov &lt;andrey.smirnov@siderolabs.com&gt;
diff --git a/go.mod b/go.mod
@@ -1,12 +1,12 @@
 module github.com/siderolabs/go-kmsg
 
-go 1.21.5
+go 1.25.0
 
 require (
-	github.com/siderolabs/gen v0.4.7
-	github.com/stretchr/testify v1.8.4
+	github.com/siderolabs/gen v0.8.6
+	github.com/stretchr/testify v1.11.1
 	go.uber.org/goleak v1.3.0
-	golang.org/x/sys v0.16.0
+	golang.org/x/sys v0.42.0
 )
 
 require (
diff --git a/go.sum b/go.sum
@@ -7,14 +7,14 @@ github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
 github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/siderolabs/gen v0.4.7 h1:lM69UYggT7yzpubf7hEFaNujPdY55Y9zvQf/NC18GvA=
-github.com/siderolabs/gen v0.4.7/go.mod h1:4PBYMdXxTg292IDRq4CGn5AymyDxJVEDvobVKDqFBEA=
-github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
-github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+github.com/siderolabs/gen v0.8.6 h1:pE6shuqov3L+5rEcAUJ/kY6iJofimljQw5G95P8a5c4=
+github.com/siderolabs/gen v0.8.6/go.mod h1:J9IbusbES2W6QWjtSHpDV9iPGZHc978h1+KJ4oQRspQ=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
 go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
 go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
-golang.org/x/sys v0.16.0 h1:xWw16ngr6ZMtmxDyKyIgsE93KNKz5HKmMa3b8ALHidU=
-golang.org/x/sys v0.16.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.42.0 h1:omrd2nAlyT5ESRdCLYdm3+fMfNFE/+Rf4bDIQImRJeo=
+golang.org/x/sys v0.42.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 h1:qIbj1fsPNlZgppZ+VLlY7N33q108Sa+fhmuc+sWQYwY=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
diff --git a/reader.go b/reader.go
@@ -68,7 +68,7 @@ func NewReader(options ...Option) (Reader, error) {
 
 	var err error
 
-	r.bootTime, err = getBootTime()
+	r.bootOffset, err = getBootTimeOffset()
 	if err != nil {
 		return nil, err
 	}
@@ -91,9 +91,9 @@ func NewReader(options ...Option) (Reader, error) {
 }
 
 type reader struct {
-	f        *os.File
-	bootTime time.Time
-	options  options
+	f          *os.File
+	bootOffset time.Duration
+	options    options
 }
 
 func (r *reader) Close() error {
@@ -148,7 +148,7 @@ func (r *reader) scanNoFollow(ctx context.Context, ch chan<- Packet) {
 		}
 
 		var packet Packet
-		packet.Message, packet.Err = ParseMessage(buf[:n], r.bootTime)
+		packet.Message, packet.Err = ParseMessage(buf[:n], time.Now().Add(r.bootOffset))
 
 		if !channel.SendWithContext(ctx, ch, packet) {
 			return
@@ -182,7 +182,7 @@ func (r *reader) scanFollow(ctx context.Context, ch chan<- Packet) {
 		}
 
 		var packet Packet
-		packet.Message, packet.Err = ParseMessage(buf[:n], r.bootTime)
+		packet.Message, packet.Err = ParseMessage(buf[:n], time.Now().Add(r.bootOffset))
 
 		if !channel.SendWithContext(ctx, ch, packet) {
 			return
diff --git a/utils_bsd.go b/utils_bsd.go
@@ -13,11 +13,11 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-func getBootTime() (time.Time, error) {
+func getBootTimeOffset() (time.Duration, error) {
 	timeval, err := unix.SysctlTimeval("kern.boottime")
 	if err != nil {
-		return time.Time{}, fmt.Errorf("could not get boot time: %w", err)
+		return 0, fmt.Errorf("could not get boot time: %w", err)
 	}
 
-	return time.Unix(timeval.Unix()), nil
+	return time.Until(time.Unix(timeval.Unix())), nil
 }
diff --git a/utils_linux.go b/utils_linux.go
@@ -13,14 +13,14 @@ import (
 	"golang.org/x/sys/unix"
 )
 
-func getBootTime() (time.Time, error) {
+func getBootTimeOffset() (time.Duration, error) {
 	var sysinfo unix.Sysinfo_t
 
 	err := unix.Sysinfo(&sysinfo)
 	if err != nil {
-		return time.Time{}, fmt.Errorf("could not get boot time: %w", err)
+		return 0, fmt.Errorf("could not get boot time: %w", err)
 	}
 
 	// sysinfo only has seconds
-	return time.Now().Add(-1 * (time.Duration(sysinfo.Uptime) * time.Second)), nil
+	return -1 * (time.Duration(sysinfo.Uptime) * time.Second), nil
 }

Original file line number	Diff line number	Diff line change
`@@ -68,7 +68,7 @@ func NewReader(options ...Option) (Reader, error) {`
`68`	`68`
`69`	`69`	`var err error`
`70`	`70`
`71`		`- r.bootTime, err = getBootTime()`
	`71`	`+ r.bootOffset, err = getBootTimeOffset()`
`72`	`72`	`if err != nil {`
`73`	`73`	`return nil, err`
`74`	`74`	`}`
`@@ -91,9 +91,9 @@ func NewReader(options ...Option) (Reader, error) {`
`91`	`91`	`}`
`92`	`92`
`93`	`93`	`type reader struct {`
`94`		`- f *os.File`
`95`		`- bootTime time.Time`
`96`		`- options options`
	`94`	`+ f *os.File`
	`95`	`+ bootOffset time.Duration`
	`96`	`+ options options`
`97`	`97`	`}`
`98`	`98`
`99`	`99`	`func (r *reader) Close() error {`
`@@ -148,7 +148,7 @@ func (r *reader) scanNoFollow(ctx context.Context, ch chan<- Packet) {`
`148`	`148`	`}`
`149`	`149`
`150`	`150`	`var packet Packet`
`151`		`- packet.Message, packet.Err = ParseMessage(buf[:n], r.bootTime)`
	`151`	`+ packet.Message, packet.Err = ParseMessage(buf[:n], time.Now().Add(r.bootOffset))`
`152`	`152`
`153`	`153`	`if !channel.SendWithContext(ctx, ch, packet) {`
`154`	`154`	`return`
`@@ -182,7 +182,7 @@ func (r *reader) scanFollow(ctx context.Context, ch chan<- Packet) {`
`182`	`182`	`}`
`183`	`183`
`184`	`184`	`var packet Packet`
`185`		`- packet.Message, packet.Err = ParseMessage(buf[:n], r.bootTime)`
	`185`	`+ packet.Message, packet.Err = ParseMessage(buf[:n], time.Now().Add(r.bootOffset))`
`186`	`186`
`187`	`187`	`if !channel.SendWithContext(ctx, ch, packet) {`
`188`	`188`	`return`
Original file line number	Diff line number	Diff line change
`@@ -13,11 +13,11 @@ import (`
`13`	`13`	`"golang.org/x/sys/unix"`
`14`	`14`	`)`
`15`	`15`
`16`		`-func getBootTime() (time.Time, error) {`
	`16`	`+func getBootTimeOffset() (time.Duration, error) {`
`17`	`17`	`timeval, err := unix.SysctlTimeval("kern.boottime")`
`18`	`18`	`if err != nil {`
`19`		`- return time.Time{}, fmt.Errorf("could not get boot time: %w", err)`
	`19`	`+ return 0, fmt.Errorf("could not get boot time: %w", err)`
`20`	`20`	`}`
`21`	`21`
`22`		`- return time.Unix(timeval.Unix()), nil`
	`22`	`+ return time.Until(time.Unix(timeval.Unix())), nil`
`23`	`23`	`}`
Original file line number	Diff line number	Diff line change
`@@ -13,14 +13,14 @@ import (`
`13`	`13`	`"golang.org/x/sys/unix"`
`14`	`14`	`)`
`15`	`15`
`16`		`-func getBootTime() (time.Time, error) {`
	`16`	`+func getBootTimeOffset() (time.Duration, error) {`
`17`	`17`	`var sysinfo unix.Sysinfo_t`
`18`	`18`
`19`	`19`	`err := unix.Sysinfo(&sysinfo)`
`20`	`20`	`if err != nil {`
`21`		`- return time.Time{}, fmt.Errorf("could not get boot time: %w", err)`
	`21`	`+ return 0, fmt.Errorf("could not get boot time: %w", err)`
`22`	`22`	`}`
`23`	`23`
`24`	`24`	`// sysinfo only has seconds`
`25`		`- return time.Now().Add(-1 * (time.Duration(sysinfo.Uptime) * time.Second)), nil`
	`25`	`+ return -1 * (time.Duration(sysinfo.Uptime) * time.Second), nil`
`26`	`26`	`}`