[MMUSIC] actpass redux

[Eric Rescorla <[e-mail]>]

Hi folks,

RFC 5763 required (and JSEP imported) that all offers include

  a=setup:actpass

However, assuming I am reading:
  https://tools.ietf.org/html/draft-ietf-mmusic-dtls-sdp-24

correctly, S 4.2 allows the initial offer to contain anything,
though encourages actpass:

   When an offerer sends the initial offer, the offerer MUST insert an
   SDP 'setup' attribute according to the procedures in [RFC4145], and
   one or more SDP 'fingerprint' attributes according to the procedures
   in [RFC8122].  In addition, the offerer MUST insert in the offer an
   SDP 'tls-id' attribute with a unique value.

   If the offerer inserts the SDP 'setup' attribute with an 'actpass' or
   'passive' attribute value, the offerer MUST be prepared to receive a
   DTLS ClientHello message (if a new DTLS association is established by
   the answerer) from the answerer before the offerer receives the SDP
   answer.

For subequent offers, it also gives flexibility but points at 4145.


So...

1. Changing the behavior for initial offers seems like it presents
a serious interop risk, because previously you could depend on
the offer being actpass.

2. JSEP requires actpass for all offers, so at least it's stricter.


What was the rationale for these changes? Feel free to point me at the
mailing list discussion where that happened.

-Ekr
 Hi folks,

RFC 5763 required (and JSEP imported) that all offers include

  a=setup:actpass

However, assuming I am reading:
  https://tools.ietf.org/html/draft-ietf-mmusic-dtls-sdp-24

correctly, S 4.2 allows the initial offer to contain anything,
though encourages actpass:

   When an offerer sends the initial offer, the offerer MUST insert an
   SDP 'setup' attribute according to the procedures in [RFC4145], and
   one or more SDP 'fingerprint' attributes according to the procedures
   in [RFC8122].  In addition, the offerer MUST insert in the offer an
   SDP 'tls-id' attribute with a unique value.

   If the offerer inserts the SDP 'setup' attribute with an 'actpass' or
   'passive' attribute value, the offerer MUST be prepared to receive a
   DTLS ClientHello message (if a new DTLS association is established by
   the answerer) from the answerer before the offerer receives the SDP
   answer.

For subequent offers, it also gives flexibility but points at 4145.


So...

1. Changing the behavior for initial offers seems like it presents
a serious interop risk, because previously you could depend on
the offer being actpass.

2. JSEP requires actpass for all offers, so at least it's stricter.


What was the rationale for these changes? Feel free to point me at the
mailing list discussion where that happened.

-Ekr