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net: Support all valid IP_MTU_DISCOVER values for UDP and TCP#12866

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copybara-service[bot] merged 2 commits intomasterfrom
test/cl894078264
Apr 3, 2026
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net: Support all valid IP_MTU_DISCOVER values for UDP and TCP#12866
copybara-service[bot] merged 2 commits intomasterfrom
test/cl894078264

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net: Support all valid IP_MTU_DISCOVER values for UDP and TCP

The UDP endpoint only accepted PMTUDiscoveryDont and the TCP endpoint rejected PMTUDiscoveryProbe, causing QUIC libraries (quic-go) to fail when setting IP_PMTUDISC_DO or IP_PMTUDISC_PROBE on UDP sockets.

Accept all valid PMTUD strategies (DONT/WANT/DO/PROBE) for both UDP and TCP, since gVisor does not implement ICMP-based PMTU feedback, PROBE and DO are functionally equivalent — both set DF but neither updates a cached route PMTU.

Test: UdpSocketTest.SetPMTUD, TcpSocketTest.SetPMTUD
FUTURE_COPYBARA_INTEGRATE_REVIEW=#12852 from tanyifeng:net-ip-mtu-discover 03548dc

The UDP endpoint only accepted PMTUDiscoveryDont and the TCP endpoint
rejected PMTUDiscoveryProbe, causing QUIC libraries (quic-go) to fail
when setting IP_PMTUDISC_DO or IP_PMTUDISC_PROBE on UDP sockets.

Accept all valid PMTUD strategies (DONT/WANT/DO/PROBE) for both UDP
and TCP, since gVisor does not implement ICMP-based PMTU feedback,
`PROBE` and `DO` are functionally equivalent — both set DF but neither
updates a cached route PMTU.

Test: UdpSocketTest.SetPMTUD, TcpSocketTest.SetPMTUD

Signed-off-by: Tan Yifeng <yiftan@tencent.com>
@copybara-service copybara-service bot added the exported Issue was exported automatically label Apr 3, 2026
@copybara-service copybara-service bot merged commit 0f29b0e into master Apr 3, 2026
@copybara-service copybara-service bot deleted the test/cl894078264 branch April 3, 2026 21:06
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