proxy/http: Avoid getting stuck when using server-first protocols

[lrh2000]

PR #99 reduces an extra RTT when setting up the CONNECT tunnel
via http proxy, however, server-first protocols (such as MySQL)
will be unusable as v2ray keeps to wait for the client request.
This commit solves the problem by limiting the maximum waiting
time to 50 ms.

[database64128]

firstPayload = make([]byte, 0) is not needed, because you already had a nil slice with var firstPayload []byte.

[codecov-commenter]

Codecov Report

Merging #1517 (31c1a00) into master (a9bf783) will increase coverage by 0.10%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1517      +/-   ##
==========================================
+ Coverage   39.27%   39.37%   +0.10%     
==========================================
  Files         604      616      +12     
  Lines       35510    37097    +1587     
==========================================
+ Hits        13946    14608     +662     
- Misses      20026    20868     +842     
- Partials     1538     1621      +83     

Impacted Files	Coverage Δ
proxy/http/client.go	0.58% <0.00%> (-0.01%)	⬇️
proxy/shadowsocks/client.go	0.86% <ø> (ø)
proxy/trojan/client.go	1.36% <0.00%> (ø)
proxy/vless/outbound/outbound.go	1.08% <0.00%> (ø)
proxy/vmess/outbound/outbound.go	61.78% <0.00%> (ø)
app/router/router.go	27.02% <0.00%> (-2.18%)	⬇️
transport/internet/headers/http/http.go	83.54% <0.00%> (-1.90%)	⬇️
transport/internet/quic/config.pb.go	37.89% <0.00%> (-1.24%)	⬇️
proxy/shadowsocks/simplified/config.go	3.03% <0.00%> (-0.20%)	⬇️
proxy/trojan/server.go	0.33% <0.00%> (-0.06%)	⬇️
... and 43 more

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[database64128]

Also, #1292 uses 100ms for shadowsocks outbound. Maybe we should define a constant and use the same wait time for all types of outbound?

[lrh2000]

firstPayload = make([]byte, 0) is not needed, because you already had a nil slice with var firstPayload []byte.

Also, #1292 uses 100ms for shadowsocks outbound. Maybe we should define a constant and use the same wait time for all types of outbound?

Thanks for your review. Actually I'm not familiar with go... and also the codebase... Any suggestions on where should I put the constant?

[database64128]

Actually I'm not familiar with go... and also the codebase...

You did a great job already! Feel free to ask if you have any questions.

Any suggestions on where should I put the constant?

proxy/proxy.go might be a good place.

[lrh2000]

Thanks @database64128 , for your nice words and kind help! I've made the constant and you may have a look at it again.

[lrh2000]

I do not think this problem has been solved. Why did this PR get closed? It seems that I cannot even reopen it.

[xiaokangwang]

I will have a look at this pr and try to merge it before next release.

[lrh2000]

@xiaokangwang Thanks! I need this feature and now I have to manually apply the patch, which is really annoying. If any changes are needed, feel free to comment.