gnrc/rpl: float DODAG during local repair #21816
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crasbe
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Type: new feature
crasbe
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Oct 23, 2025
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I had to rebase to include the CI fix #21819. |
If the parent set of a router is empty and a local repair initiated, don't immediately poison all routes. Instead configure node as root of a new floating DODAG to maintain connectivity in the sub-tree. Once a different, grounded DODAG is found the node will join the new DODAG. If no other DODAG is found the floating DODAG will timeout after `CONFIG_GNRC_RPL_DODAG_FLOAT_TIMEOUT` and cleaned up..
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Contribution description
Add the option to create a temporary floating DODAG if the parent set of a node becomes empty and a local repair is started. This allows to maintain connectivity within the sub-tree, even if the uplink is temporarily gone (e.g., because a BLE connection broke). See RFC6550#Section18.2.4.
With #21759 merged, we now support switching between DODAGs. So as soon as the parent node (or any other node in the subtree) receives a DIO again from the original, grounded (i.e., non-floating) DODAG, it will switch back to that one. Children will furthermore not join the new floating DODAG in the first place, if they are still connected to the grounded DODAG through another parent.
A floating DODAG has a configurable timeout after which the DODAG will be cleaned up. If the timeout is set to 0, then the old logic for
gnrc_rpl_local_repairis retained. It just immediately poisons all routes (causing the local node to be cleared from the children's parent set) and cleans up the DODAG.Testing procedure
Can be tested with min. 3 nodes and the
gnrc_networkingexample with a BLE capable board.Set
CONFIG_GNRC_RPL_DEFAULT_LIFETIME=1(=1min). Until #21608 is merged, we can only detect a lost parent through a timeout mechanism.N{0..1}and connect them in a lineN0as RPL root for2001:db8::1=>N1andN2will join the DODAGN0andN1. After the 1min timeout,N1will set itself to be the root of a new floating DODAG. The DODAG ID is the public IP ofN1.N2will join the new floating DODAGN1andN2can still ping each otherN1orN2again toN0and callrpl send disN0Issues/PRs references
Part of #21574.