swanctl: Document how DH groups in CHILD_SA proposals are applied

References #1039.

diff --git a/src/swanctl/swanctl.opt b/src/swanctl/swanctl.opt
index fe5b293fb2b26768b82cc4f7a36bbb5a37589772..15cbc6cfcaa3b2cc02e4868799f34a63c7b9185c 100644 (file)
--- a/src/swanctl/swanctl.opt
+++ b/src/swanctl/swanctl.opt
@@ -472,7 +472,7 @@ connections.<conn>.children.<child>.ah_proposals =
        For AH, this includes an integrity algorithm and an optional Diffie-Hellman
        group. If a DH group is specified, CHILD_SA/Quick Mode rekeying and initial
        negotiation uses a separate Diffie-Hellman exchange using the specified
-       group.
+       group (refer to _esp_proposals_ for details).
 
        In IKEv2, multiple algorithms of the same kind can be specified in a single
        proposal, from which one gets selected. In IKEv1, only one algorithm per
@@ -495,11 +495,18 @@ connections.<conn>.children.<child>.esp_proposals = default
        mode algorithm is used instead of the separate encryption/integrity
        algorithms.
 
-       If a DH group is specified, CHILD_SA/Quick Mode rekeying and initial (non
-       IKE_AUTH piggybacked) negotiation uses a separate Diffie-Hellman exchange
-       using the specified group. Extended Sequence Number support may be indicated
-       with the _esn_ and _noesn_ values, both may be included to indicate support
-       for both modes. If omitted, _noesn_ is assumed.
+       If a DH group is specified, CHILD_SA/Quick Mode rekeying and initial
+       negotiation use a separate Diffie-Hellman exchange using the specified
+       group. However, for IKEv2, the keys of the CHILD_SA created implicitly with
+       the IKE_SA will always be derived from the IKE_SA's key material. So any DH
+       group specified here will only apply when the CHILD_SA is later rekeyed or
+       is created with a separate CREATE_CHILD_SA exchange. A proposal mismatch
+       might, therefore, not immediately be noticed when the SA is established, but
+       may later cause rekeying to fail.
+
+       Extended Sequence Number support may be indicated with the _esn_ and _noesn_
+       values, both may be included to indicate support for both modes. If omitted,
+       _noesn_ is assumed.
 
        In IKEv2, multiple algorithms of the same kind can be specified in a single
        proposal, from which one gets selected. In IKEv1, only one algorithm per