Date: Fri, 02 Jan 2015 18:36:00 +0300 From: "Alexander V. Chernikov" <melifaro@yandex-team.ru> To: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: host pipes and netmap 'emulated mode' Message-ID: <54A6BAE0.9020404@yandex-team.ru>
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Hello list. It looks like it is impossible to use host pipes and emulated netmap mode in some cases. For example, if you're doing something like what traditional router do: packet processing, with kernel-visible logical interfaces, routing daemon running there, you can easily get a panic like this: #0 0xffffffff8094aa76 at kdb_backtrace+0x66 #1 0xffffffff809104ee at panic+0x1ce #2 0xffffffff80cf9660 at trap_fatal+0x290 #3 0xffffffff80cf99c1 at trap_pfault+0x211 #4 0xffffffff80cf9f89 at trap+0x329 #5 0xffffffff80ce30d3 at calltrap+0x8 #6 0xffffffff809d3b5f at ether_demux+0x6f #7 0xffffffff809d3f34 at ether_nh_input+0x204 #8 0xffffffff809dd6d8 at netisr_dispatch_src+0x218 #9 0xffffffff8061b2b5 at netmap_send_up+0x35 #10 0xffffffff8061b3d7 at netmap_txsync_to_host+0x97 #11 0xffffffff8061b400 at netmap_txsync_to_host_compat+0x10 #12 0xffffffff8061de8c at netmap_poll+0x2fc #13 0xffffffff807f2313 at devfs_poll_f+0x63 #14 0xffffffff8095ea3d at sys_poll+0x35d #15 0xffffffff80cf8e0a at amd64_syscall+0x5ea #16 0xffffffff80ce33b7 at Xfast_syscall+0xf7 Uptime: 4m21s The problem here is the following: netmap changes if_input() for the logical network interface and always assumes that generic_rx_handler() is called with netmap-enabled ifp (e.g. original inteface). Unfortunately, there are cases where we have different ifp passed to if_input handler. This particular case is triggered by (*ifp->if_input)(ifv->ifv_ifp, m); line, where "ifp" represents netmap-enabled NIC, and ifv->ifv_ifp represents vlan subinterface. Then, generic_rx_handler() tries to looking NA/GNA structure but fails since vlan subinterface is not netmap-enabled. So, it looks like that we need a way to call original if_input() but I can't imagine (good) one/
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