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hotfix(pmtud): increase TCP margin from 150 to 300 compared to ICMP found MTU

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This commit is contained in:
Quentin McGaw
2026-02-19 17:24:06 +00:00
parent c6b211ef9b
commit 007c5159f4
2 changed files with 9 additions and 5 deletions
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internal/pmtud/pmtud.go
+4 -3
View File
@@ -13,7 +13,7 @@ import (
"github.com/qdm12/gluetun/internal/pmtud/tcp" "github.com/qdm12/gluetun/internal/pmtud/tcp"
) )
var ErrPMTUDFailICMPAndTCP = errors.New("PMTUD failed with both ICMP and TCP") var ErrPMTUDFailICMPAndTCP = errors.New("PMTUD succeeded with ICMP but failed with TCP")
// PathMTUDiscover discovers the maximum MTU using both ICMP and TCP. // PathMTUDiscover discovers the maximum MTU using both ICMP and TCP.
// Multiple ICMP addresses and TCP addresses can be specified for redundancy. // Multiple ICMP addresses and TCP addresses can be specified for redundancy.
@@ -66,7 +66,7 @@ func PathMTUDiscover(ctx context.Context, icmpAddrs []netip.Addr, tcpAddrs []net
minMTU = constants.MinIPv6MTU minMTU = constants.MinIPv6MTU
} }
if icmpSuccess { if icmpSuccess {
const mtuMargin = 150 const mtuMargin = 300
minMTU = max(maxPossibleMTU-mtuMargin, minMTU) minMTU = max(maxPossibleMTU-mtuMargin, minMTU)
} }
mtu, err = tcp.PathMTUDiscover(ctx, tcpAddrs, minMTU, maxPossibleMTU, tryTimeout, fw, logger) mtu, err = tcp.PathMTUDiscover(ctx, tcpAddrs, minMTU, maxPossibleMTU, tryTimeout, fw, logger)
@@ -77,7 +77,8 @@ func PathMTUDiscover(ctx context.Context, icmpAddrs []netip.Addr, tcpAddrs []net
return maxPossibleMTU, nil // only rely on ICMP PMTUD results return maxPossibleMTU, nil // only rely on ICMP PMTUD results
} }
} }
return 0, fmt.Errorf("%w", ErrPMTUDFailICMPAndTCP) return 0, fmt.Errorf("%w - ignoring ICMP obtained MTU %d",
ErrPMTUDFailICMPAndTCP, maxPossibleMTU)
} }
logger.Debugf("TCP path MTU discovery found maximum valid MTU %d", mtu) logger.Debugf("TCP path MTU discovery found maximum valid MTU %d", mtu)
return mtu, nil return mtu, nil
internal/pmtud/test/mtu.go
+5 -2
View File
@@ -1,6 +1,9 @@
package test package test
import "math" import (
"fmt"
"math"
)
// MakeMTUsToTest determines a slice of MTU values to test // MakeMTUsToTest determines a slice of MTU values to test
// between minMTU and maxMTU inclusive. It creates an MTU // between minMTU and maxMTU inclusive. It creates an MTU
@@ -17,7 +20,7 @@ func MakeMTUsToTest(minMTU, maxMTU uint32) (mtus []uint32) {
diff := maxMTU - minMTU diff := maxMTU - minMTU
switch { switch {
case minMTU > maxMTU: case minMTU > maxMTU:
panic("minMTU > maxMTU") panic(fmt.Sprintf("minMTU %d is greater than maxMTU %d", minMTU, maxMTU))
case diff <= mtusLength: case diff <= mtusLength:
mtus = make([]uint32, 0, diff) mtus = make([]uint32, 0, diff)
for mtu := minMTU; mtu <= maxMTU; mtu++ { for mtu := minMTU; mtu <= maxMTU; mtu++ {