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net: Replace ifname check with IFF_LOOPBACK in Discover #29984

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merged 2 commits into from
May 7, 2024
Merged

net: Replace ifname check with IFF_LOOPBACK in Discover #29984

merged 2 commits into from
May 7, 2024

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laanwj
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@laanwj laanwj commented Apr 28, 2024 •
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Checking the interface name is kind of brittle. In the age of network namespaces and containers, there is no reason a loopback interface can't be called differently.

Check for the IFF_LOOPBACK flag to detect loopback interface instead.

Also remove a misleading comment in Discover's doc comment.

@laanwj
net: Replace ifname check with IFF_LOOPBACK in Discover
7766dd2 
Checking the interface name is kind of brittle. In the age of network
namespaces and containers, there is no reason a loopback interface can't
be called differently.

Check for the `IFF_LOOPBACK` flag to detect loopback interface instead.
@laanwj laanwj added the P2P label Apr 28, 2024
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DrahtBot commented Apr 28, 2024 •
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The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

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For detailed information about the code coverage, see the test coverage report.

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ACK sipa, willcl-ark, theuni

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Conflicts

Reviewers, this pull request conflicts with the following ones:

  • #30043 (net: Replace libnatpmp with built-in PCP implementation by laanwj)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

@laanwj
net: Fix misleading comment for Discover
a68fed1 
All network addresses are being iterated over and added, not just the first one per interface.
@sipa
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sipa commented Apr 28, 2024

utACK a68fed1

willcl-ark
willcl-ark approved these changes Apr 30, 2024
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utACK a68fed1

Agree this will be less brittle than name-checking. I don't think it's possible that IFF_LOOPBACK would ever be unset for a loopback device unless someone had modified their kernel.

@DrahtBot DrahtBot mentioned this pull request May 6, 2024
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theuni
theuni approved these changes May 6, 2024
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utACK a68fed1. Satoshi-era brittleness :)

@fanquake fanquake merged commit ef09f53 into bitcoin:master May 7, 2024
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theStack commented May 7, 2024

post-merge ACK a68fed1

Interestingly, libpcap still implements both the "brittle" and the IFF_LOOPBACK flag way to detect loopback devices (https://github.com/the-tcpdump-group/libpcap/blob/0797ed7340f93618fd097ad870dfc1dde7cecc4f/pcap.c#L1042-L1053), but the code was seemingly introduced in 1998 (https://github.com/the-tcpdump-group/libpcap/blob/0797ed7340f93618fd097ad870dfc1dde7cecc4f/CHANGES#L1443-L1445) and I suspect that these days you won't find any Unix-like OS anymore that does not provide IFF_LOOPBACK.

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laanwj commented May 8, 2024

Thanks for checking! it's kind of a belt-and-suspenders check: we only look for routable addresses in Discover, so unless someone assigned a routable address to the loopback interface-which would be really strange-it doesn't actually influence the result.

PastaPastaPasta pushed a commit to PastaPastaPasta/dash that referenced this pull request Oct 25, 2024
@fanquake @PastaPastaPasta
Merge bitcoin#29984: net: Replace ifname check with IFF_LOOPBACK in D…
c239864 
…iscover

a68fed1 net: Fix misleading comment for Discover (laanwj)
7766dd2 net: Replace ifname check with IFF_LOOPBACK in Discover (laanwj)

Pull request description:

  Checking the interface name is kind of brittle. In the age of network namespaces and containers, there is no reason a loopback interface can't be called differently.

  Check for the `IFF_LOOPBACK` flag to detect loopback interface instead.

  Also remove a misleading comment in Discover's doc comment.

ACKs for top commit:
  sipa:
    utACK a68fed1
  willcl-ark:
    utACK a68fed1
  theuni:
    utACK a68fed1. Satoshi-era brittleness :)

Tree-SHA512: e2d7fc541f40f6a6af08286e7bcb0873ff55debdcd8b38b03f274897b673a6fb51d84d6c7241a02a9567ddf2645f50231d91bb1f55307ba7c6e68196c29b0edf
PastaPastaPasta pushed a commit to PastaPastaPasta/dash that referenced this pull request Oct 26, 2024
@fanquake @PastaPastaPasta
Merge bitcoin#29984: net: Replace ifname check with IFF_LOOPBACK in D…
f1907ea 
…iscover

a68fed1 net: Fix misleading comment for Discover (laanwj)
7766dd2 net: Replace ifname check with IFF_LOOPBACK in Discover (laanwj)

Pull request description:

  Checking the interface name is kind of brittle. In the age of network namespaces and containers, there is no reason a loopback interface can't be called differently.

  Check for the `IFF_LOOPBACK` flag to detect loopback interface instead.

  Also remove a misleading comment in Discover's doc comment.

ACKs for top commit:
  sipa:
    utACK a68fed1
  willcl-ark:
    utACK a68fed1
  theuni:
    utACK a68fed1. Satoshi-era brittleness :)

Tree-SHA512: e2d7fc541f40f6a6af08286e7bcb0873ff55debdcd8b38b03f274897b673a6fb51d84d6c7241a02a9567ddf2645f50231d91bb1f55307ba7c6e68196c29b0edf
PastaPastaPasta added a commit to dashpay/dash that referenced this pull request Oct 27, 2024
@PastaPastaPasta
Merge #6363: backport: trivial 2024 10 25 pr2
f211bb9 
700b8c5 Merge bitcoin#29658: Bugfix: GUI: Help messages already have a trailing newline, so don't add an extra one (merge-script)
a0cd305 Merge bitcoin#29948: test: add missing comparison of node1's mempool in MempoolPackagesTest (Ava Chow)
f1907ea Merge bitcoin#29984: net: Replace ifname check with IFF_LOOPBACK in Discover (merge-script)
daa6eee Merge bitcoin#29960: depends: pass verbose through to cmake based makefiles (merge-script)
61a5832 Merge bitcoin#29907: test: Fix `test/streams_tests.cpp` compilation on SunOS / illumos (merge-script)
23f25a9 Merge bitcoin#29872: test: Add missing Assert(mock_time_in >= 0s) to SetMockTime (merge-script)
a7daee7 Merge bitcoin#29689: lint: scripted-diff verification also requires GNU grep (Ava Chow)
3df1ca1 Merge bitcoin#29953: doc: Bash is needed in gen_id and is not installed on FreeBSD by default (merge-script)
b53b854 Merge bitcoin#29850: net: Decrease nMaxIPs when learning from DNS seeds (Ava Chow)
c4a147c Merge bitcoin#28340: security: restrict abis in bitcoind.service (Ryan Ofsky)
acfdf9e Merge bitcoin#28373: doc: Add example of mixing private and public keys in descriptors (Ava Chow)
51bc8bd Merge bitcoin#29859: build: Fix false positive `CHECK_ATOMIC` test (merge-script)
bb4102c Merge bitcoin#29893: test: fix intermittent failure in p2p_compactblocks_hb.py (glozow)
4ecb761 Merge bitcoin#29786: Drop Windows Socket dependency for `randomenv.cpp` (fanquake)
1a8e805 Merge bitcoin#29498: test: Update --tmpdir doc string to say directory must not exist (fanquake)
81ca71c Merge bitcoin#29781: depends: add new LLVM debug macro (fanquake)
5ce92ca Merge bitcoin#29527: depends: add -g to DEBUG=1 flags (fanquake)

Pull request description:

  ## Issue being fixed or feature implemented
  Trivial backports

  ## What was done?

  ## How Has This Been Tested?
  built locally

  ## Breaking Changes

  ## Checklist:
    _Go over all the following points, and put an `x` in all the boxes that apply._
  - [ ] I have performed a self-review of my own code
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have added or updated relevant unit/integration/functional/e2e tests
  - [ ] I have made corresponding changes to the documentation
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

ACKs for top commit:
  UdjinM6:
    utACK 700b8c5 but pls confirm Guix is happy now before merging
  kwvg:
    utACK 700b8c5

Tree-SHA512: 9722979c4f0589cb02bfeaf39373713372a4aa1c8c5a55aa5b4d33388f73ef19231de3963b80ffaad25fbe0db90a133de5080baac691daed41b86a762b867b2d
@andremralves andremralves mentioned this pull request Nov 20, 2024
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@willcl-ark willcl-ark willcl-ark approved these changes

@theuni theuni theuni approved these changes

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@laanwj @DrahtBot @sipa @theStack @theuni @willcl-ark @fanquake