On 29 November 2015 at 05:06, Haggai Eran <hagg...@mellanox.com> wrote: > On 14/11/2015 08:45, Joe Stringer wrote: >> On 13 November 2015 at 06:46, Or Gerlitz <gerlitz...@gmail.com> wrote: >>> > On Fri, Nov 13, 2015 at 10:14 AM, Joe Stringer <joestrin...@nicira.com> >>> > wrote: >>> > >>>> >> I don't follow the logic. You observed one flow which matched on >>>> >> TTL=64, therefore all vxlan packets terminated at OVS have TTL=64? >>> > >>>> >> If OVS received packets with different TTLs, they would miss and >>>> >> ovs-vswitchd would generate flows to match that traffic too. >>> > >>> > ok, that makes things a bit better, but (see next) >>> > >>>> >> If that becomes an issue, presumably the wildcard generation can be >>>> >> improved. >>> > >>> > is there a deep reason for vlxan "learned flows" to actually match w >>> > or w.o wild cards on TTLs?? for non-tunneled flow I don't see this >>> > happening. >> No deep reason I'm aware of. > > Hi, > > We looked into the OVS kernel module, and apparently there's a check > that rejects new tunnel flows if they don't have the TTL mask set [1]. > > I was able to trace it to this commit [2] on the OVS tree, but I don't > quite understand why the check was added. There was some discussion > about the patch on the mailing list [3] that hints this was about > catching zero TTL, but it has too little context for me to understand. > > I'm adding the author and reviewer of the patch, perhaps they can help > explain this requirement.
I'm not the author or reviewer, but it seems like this is an attempt to prevent flows from matching TTL=0 then proceeding to forward the frame. You could still match a non-zero TTL with a wildcarded mask, but it wouldn't be possible for a single flow to match all (non-zero) TTL values. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
