Bugzilla – Bug 732
tcp-mss, outgoing-tcp-mss option
Last modified: 2016-01-05 11:40:07 CET
Created attachment 312 [details]
I have created a patch to add two options, tcp-mss and outgoing-tcp-mss to set TCP MSS via setsockopt(TCP_MAXSEG). When PMTUD doesn't work correctly, setting TCP MSS to value lower than common MSS on ethernet would help.
Maximum segment size (MSS) of TCP socket on which the server
responds to queries.
Maximum segment size (MSS) of TCP socket for outgoing XFR
request to other namesevers.
PMTUD doesn't work under ECMP server load-balancing or anycast deployment in some cases. Reducing TCP MSS is easy and suitable method for DNS servers to address this issue.
I have tested this patch on Ubuntu12, CentOS7, and FreeBSD10. But on FreeBSD setsockopt(TCP_MAXSEG) is implemented but it doesn't work .
I submitted same patch for Unbound
Thank you for your patch. I have applied it to the code repository.
Best regards, Wouter