request: in the event of failure, try other IPs (#6761) (#6813)

* request: in the event of failure, try other IPs (#6761)

In the case where a name has multiple A/AAAA records, we should
try subsequent records instead of immediately failing when we have a
failure on the first IP address.

This significantly improves delivery success when there are network
connectivity problems affecting only IPv4 or IPv6.

* fix method call style

* request_spec: adjust test case to use Addrinfo

* request: Request/open: move private addr check to within begin/rescue

* request_spec: add case to test failover, fix exception check

* Double Addrinfo.foreach so that it correctly yields instances

2 files changed, 20 insertions, 4 deletions

diff --git a/app/lib/request.rb b/app/lib/request.rb
index 5776b3d78..298fb9528 100644
--- a/app/lib/request.rb
+++ b/app/lib/request.rb
@@ -94,9 +94,16 @@ class Request
   class Socket < TCPSocket
     class << self
       def open(host, *args)
-        address = IPSocket.getaddress(host)
-        raise Mastodon::HostValidationError if PrivateAddressCheck.private_address? IPAddr.new(address)
-        super address, *args
+        outer_e = nil
+        Addrinfo.foreach(host, nil, nil, :SOCK_STREAM) do |address|
+          begin
+            raise Mastodon::HostValidationError if PrivateAddressCheck.private_address? IPAddr.new(address.ip_address)
+            return super address.ip_address, *args
+          rescue => e
+            outer_e = e
+          end
+        end
+        raise outer_e if outer_e
       end
 
       alias new open
diff --git a/spec/lib/request_spec.rb b/spec/lib/request_spec.rb
index dc7daa52c..5da357c55 100644
--- a/spec/lib/request_spec.rb
+++ b/spec/lib/request_spec.rb
@@ -48,6 +48,13 @@ describe Request do
         expect(a_request(:get, 'http://example.com')).to have_been_made.once
       end
 
+      it 'executes a HTTP request when the first address is private' do
+        allow(Addrinfo).to receive(:foreach).with('example.com', nil, nil, :SOCK_STREAM)
+                                            .and_yield(Addrinfo.new(["AF_INET", 0, "example.com", "0.0.0.0"], :PF_INET, :SOCK_STREAM))
+                                            .and_yield(Addrinfo.new(["AF_INET6", 0, "example.com", "2001:4860:4860::8844"], :PF_INET6, :SOCK_STREAM))
+        expect(a_request(:get, 'http://example.com')).to have_been_made.once
+      end
+
       it 'sets headers' do
         expect(a_request(:get, 'http://example.com').with(headers: subject.headers)).to have_been_made
       end
@@ -61,7 +68,9 @@ describe Request do
       end
 
       it 'raises Mastodon::ValidationError' do
-        allow(IPSocket).to receive(:getaddress).with('example.com').and_return('0.0.0.0')
+        allow(Addrinfo).to receive(:foreach).with('example.com', nil, nil, :SOCK_STREAM)
+                                            .and_yield(Addrinfo.new(["AF_INET", 0, "example.com", "0.0.0.0"], :PF_INET, :SOCK_STREAM))
+                                            .and_yield(Addrinfo.new(["AF_INET6", 0, "example.com", "2001:db8::face"], :PF_INET6, :SOCK_STREAM))
         expect{ subject.perform }.to raise_error Mastodon::ValidationError
       end
     end