Add network PMTU support #80993
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Add network PMTU support #80993
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Note to self, the fragmentation code in both IPv4 and IPv6 needs some additional checks for PMTU. Need to fix that after 4.0 is released. |
rlubos
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Nov 12, 2024
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Looks good, impressive work!
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Marking this as WIP/DNM as I need to implement these features:
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This adds generic code that can be used by both IPv4 and IPv6 Path MTU Discovery mechanism. The actual PMTU support for each protocol family is in subsequent commits. Signed-off-by: Jukka Rissanen <[email protected]>
Add initial tests for generic part of PMTU discovery code. Signed-off-by: Jukka Rissanen <[email protected]>
Add information about PMTU related packets received/sent/dropped for IPv6. Signed-off-by: Jukka Rissanen <[email protected]>
Print more cases when the packet is dropped, and also print the upper layer verdict for the packet. Signed-off-by: Jukka Rissanen <[email protected]>
Catch "Packet Too Big" ICMPv6 messages and update PMTU for a given destination IPv6 address. Use that PMTU when sending data to the destination. Signed-off-by: Jukka Rissanen <[email protected]>
Allow tests to check whether a IPv6 TCP connection MTU is changed. Signed-off-by: Jukka Rissanen <[email protected]>
Show information whether PMTU is enabled or not. Show pmtu destination cache content with "net pmtu" command. The "net pmtu flush" can be used to clear the cache. Signed-off-by: Jukka Rissanen <[email protected]>
Add information about PMTU related packets received/sent/dropped for IPv4. Signed-off-by: Jukka Rissanen <[email protected]>
Catch "Destination Unreachable" ICMPv4 messages and update PMTU for a given destination IPv4 address. Use that PMTU when sending data to the destination. Signed-off-by: Jukka Rissanen <[email protected]>
Allow tests to check whether a IPv4 TCP connection MTU is changed. Signed-off-by: Jukka Rissanen <[email protected]>
Send a network management event for a changed path MTU value. Both IPv4 and IPv6 have their own events as we cannot mix these because how the network event numbering space is implemented. Signed-off-by: Jukka Rissanen <[email protected]>
Verify that the PMTU changed events are generated and we can catch them. Signed-off-by: Jukka Rissanen <[email protected]>
Print the changed PMTU value and IP address in the event monitor. Signed-off-by: Jukka Rissanen <[email protected]>
Set the commands to monitor correctly. Before this change some events were missed. Signed-off-by: Jukka Rissanen <[email protected]>
Add IP_MTU IPv4 socket option and implement getsockopt() call for the option. The IP_MTU option does not support setsockopt() call. Signed-off-by: Jukka Rissanen <[email protected]>
Make sure we can use IP_MTU socket option from application. Signed-off-by: Jukka Rissanen <[email protected]>
Add IPV6_MTU IPv6 socket option and implement getsockopt() and setsockopt() calls for the option. Signed-off-by: Jukka Rissanen <[email protected]>
Make sure we can use IPV6_MTU socket option from application. Signed-off-by: Jukka Rissanen <[email protected]>
If PMTU is enabled, then use the MTU value from it instead of always using network interface MTU. Signed-off-by: Jukka Rissanen <[email protected]>
Enable PMTU so that we test it with IPv4 fragmentation code. Signed-off-by: Jukka Rissanen <[email protected]>
Shorten the timeouts so that the tests are run in 6 second instead of 15 seconds. Use only native_sim for the tests so that the tests are run without any extra delays. Signed-off-by: Jukka Rissanen <[email protected]>
If PMTU is enabled, then use the MTU value from it instead of always using network interface MTU. Signed-off-by: Jukka Rissanen <[email protected]>
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rlubos
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nit; Typo in the commit message: tests: net: ipvr6_fragment: -> tests: net: ipv6_fragment:
Enable PMTU so that we test it with IPv6 fragmentation code. Signed-off-by: Jukka Rissanen <[email protected]>
After we take the true MTU into account, we need to send proper number of bytes (multiple of 8) in one IPv6 fragment. Signed-off-by: Jukka Rissanen <[email protected]>
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@pdgendt if you have time, please take a look. |
pdgendt
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Nov 18, 2024
| #define NET_IPV6_PMTU_ENTRIES 0 | ||
| #endif | ||
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| #define NET_PMTU_MAX_ENTRIES (NET_IPV4_PMTU_ENTRIES + NET_IPV6_PMTU_ENTRIES) |
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Minor hidden detail, the number of cache entries each get a maximum option setting, however AFAICS the entries are shared between IPv4 and IPv6?
So if both are set to 3, you could have 6 IPv4 and 0 IPv6 entries? Or am I missing something?
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The cache is shared between IPv4 and IPv6 entries in order to utilize the cache better. If the cache is "full", the oldest entry is re-used be it IPv4 or IPv6. We could certainly separate the IPv4 and IPv6 entries to individual caches, but I think it would just use more memory without extra benefits.
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This implements IPv4 and IPv6 Path MTU Discovery support.
See https://www.rfc-editor.org/rfc/rfc1191 for IPv4 and
https://www.rfc-editor.org/rfc/rfc8201 for IPv6
General PMTU information can be found here https://en.wikipedia.org/wiki/Path_MTU_Discovery
Original issue here #2302