debugnet(4): Infer non-server connection parameters
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Authored by cem on Sep 1 2019, 8:38 AM.

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emaste
markj

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manpages

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rS353694: debugnet(4): Infer non-server connection parameters

Summary

Loosen requirements for connecting to debugnet-type servers. Only require a
destination address; the rest can theoretically be inferred from the routing
table. (If the routing table is potentially damaged, one can always specify
the parameters explicitly with the same option flags as before.

Relax corresponding constraints in netdump(4) and move ifp validation to
debugnet connection time.

Submitted by: John Reimer <john.reimer AT emc.com> (earlier version)

Test Plan

testvm# sysctl debug.kdb.panic=1
debug.kdb.panic:panic: kdb_sysctl_panic
...
KDB: enter: panic
[ thread pid 697 tid 100102 ]
Stopped at      kdb_enter.part.5+0x27:  movq    $0,0x139348e(%rip)
db> netdump -s x.y.z.d debugnet: overwriting mbuf zone pointers
debugnet_connect: Destination address is on link.
debugnet_connect: Connecting to x.y.z.d:20023 from a.b.c.d:20024 on vtnet0
debugnet_connect: searching for server MAC...
debugnet_handle_arp: got server MAC address aa:bb:cc:dd:ee:ff
netdumping to x.y.z.d (aa:bb:cc:dd:ee:ff)
Dumping 96 out of 475 MB:..17% ..34%..50%..67% ..84%..100%
netdump finished.
debugnet: restoring mbuf zone pointers

Dump complete

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Build Status

Buildable 26218
Build 24716: arc lint + arc unit

Event Timeline

cem created this revision.Sep 1 2019, 8:38 AM

Herald added a subscriber: ae. · View Herald TranscriptSep 1 2019, 8:38 AM

Harbormaster completed remote builds in B26218: Diff 61523.Sep 1 2019, 8:38 AM

cem added a parent revision: D21460: Add ddb(4) 'netdump' command to netdump a core without preconfiguration.Sep 3 2019, 10:52 PM

Rebase on lexer API change.

Harbormaster completed remote builds in B26266: Diff 61632.Sep 4 2019, 12:24 AM

cem added a child revision: D21541: debugnet(4): Add optional full-duplex mode.Sep 6 2019, 12:55 AM

cem added a child revision: D21568: Implement NetGDB(4).Sep 9 2019, 4:21 PM

markj added inline comments.Sep 10 2019, 12:42 AM

sys/netinet/netdump/netdump_client.c
414	This check doesn't really make sense for a DDB-invoked netdump. The panicking thread may well be in a non-default vnet, in which case we should switch to vnet0 for the purpose of the lookup, like you do for the routing table lookup above. For configuration coming from dumpon I think it still makes sense for now to reject the request when running in vnet0.