One other optimization that I omitted from that note: The common substring cannot be longer than the From domain, and we discard any where the common substring is shorter than the organizational domain. Therefore, the common substring is always an aligned domain! (The primary tree walk has already scanned the path between the From domain and Organizational domain.)
We don't need a tree walk for parent domains, because the common substring will be the entire candidate domain, and therefore aligned. Because the common substring is aligned, when performing a tree walk for child and sibling domains, we only need to walk up from the candidate domain to the common substring. This involves less processing than if we had to walk all the way up to the organizational domain. Doug On Wed, Mar 23, 2022 at 6:59 AM Alessandro Vesely <[email protected]> wrote: > Hm... > > On Wed 23/Mar/2022 03:08:35 +0100 Douglas Foster wrote: > > During my ruminations last night, I gained some clarity around that > > question and wanted to highlight those conclusions. They simplify the > > alignment search significantly: > > > > - If the common substring is shorter than the Organizational Domain, > then the > > names are not aligned and the candidate domain can be ignored. > > > > - Otherwise, if any candidate domain is a parent of (or equal to) the > FROM > > domain, then and we have alignment and DMARC PASS. The secondary tree > walk is > > not needed and no further evaluation is required. > > > > - If several candidate names are child domains of the FROM address, then > only > > the shortest string needs to be evaluated with a secondary tree walk. > If it is > > aligned, further evaluation is not required. If it is not aligned > because of > > an organizational boundary, all other child domains are also excluded. > > > That and the deeper-than-5 optimization Doug posted on a separate message. > > > I know the document is already longish. However, collecting these > observations > in an appendix may be helpful for developers, and maybe also for general > understanding of the intricacies involved in the tree walk, including > proper > usage of the psd= flag. > > > Best > Ale > -- > > > > > _______________________________________________ > dmarc mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/dmarc >
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