Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

It's always TCP_NODELAY

brooker.co.za

Post reply on HN
Print view View original

21–30 of 276 posts

Re: It's always TCP_NODELAY

#21

Post by coldpie »

batmanthehorse wrote: post #17

Does anyone know of a good way to enable TCP_NODELAY on sockets when you don't have access to the source for that application? I can't find any kernel settings to make it permanent, or commands to change it after the fact. I've been able to disable delayed acks using `quickack 1` in the routing table, but it seems particularly hard to enable TCP_NODELAY from outside the application. I've been having exactly the probl…

Would some kind of LD_PRELOAD interception for socket(2) work? Call the real function, then do setsockopt or whatever, and return the modified socket.

Re: It's always TCP_NODELAY

#22

Post by loopdoend »

theamk wrote: post #2

I don't by the reasoning for never needing Nagle anymore. Sure, telnet isn't a thing today, but I bet there are still plenty of apps which do equivalent of: write(fd, "Host: ") write(fd, hostname) write(fd, "\r\n") write(fd, "Content-type: ") etc... this may not be 40x overhead, but it'd still 5x or so.

Ah yeah I fixed this exact bug in net-http in Ruby core a decade ago.

Re: It's always TCP_NODELAY

#24

Post by p_l »

obelos wrote: post #7

Not every time. Sometimes it's DNS.

Once it was a failing line card in router zeroing last bit in IPv4 addresses, resulting in ticket about "only even IPv4 addresses are accessible" ...

Re: It's always TCP_NODELAY

#25

Post by tptacek »

theamk wrote: post #2

I don't by the reasoning for never needing Nagle anymore. Sure, telnet isn't a thing today, but I bet there are still plenty of apps which do equivalent of: write(fd, "Host: ") write(fd, hostname) write(fd, "\r\n") write(fd, "Content-type: ") etc... this may not be 40x overhead, but it'd still 5x or so.

The discussion here mostly seems to miss the point. The argument is to change the default, not to eliminate the behavior altogether.

Re: It's always TCP_NODELAY

#26

Post by praptak »

batmanthehorse wrote: post #17

Does anyone know of a good way to enable TCP_NODELAY on sockets when you don't have access to the source for that application? I can't find any kernel settings to make it permanent, or commands to change it after the fact. I've been able to disable delayed acks using `quickack 1` in the routing table, but it seems particularly hard to enable TCP_NODELAY from outside the application. I've been having exactly the probl…

Attach debugger (ptrace), call setsockopt?

Re: It's always TCP_NODELAY

#27

Post by batmanthehorse »

tedunangst wrote: post #18
batmanthehorse wrote: post #17

Does anyone know of a good way to enable TCP_NODELAY on sockets when you don't have access to the source for that application? I can't find any kernel settings to make it permanent, or commands to change it after the fact. I've been able to disable delayed acks using `quickack 1` in the routing table, but it seems particularly hard to enable TCP_NODELAY from outside the application. I've been having exactly the probl…

LD_PRELOAD.

Thank you, found this: https://github.com/sschroe/libnodelay

Re: It's always TCP_NODELAY

#28

Post by cesarb »

coldpie wrote: post #21
batmanthehorse wrote: post #17

Does anyone know of a good way to enable TCP_NODELAY on sockets when you don't have access to the source for that application? I can't find any kernel settings to make it permanent, or commands to change it after the fact. I've been able to disable delayed acks using `quickack 1` in the routing table, but it seems particularly hard to enable TCP_NODELAY from outside the application. I've been having exactly the probl…

Would some kind of LD_PRELOAD interception for socket(2) work? Call the real function, then do setsockopt or whatever, and return the modified socket.

> Would some kind of LD_PRELOAD interception for socket(2) work?

That would only work if the call goes through libc, and it's not statically linked. However, it's becoming more and more common to do system calls directly, bypassing libc; the Go language is infamous for doing that, but there's also things like the rustix crate for Rust (https://crates.io/crates/rustix), which does direct system calls by default.

Re: It's always TCP_NODELAY

#30

Post by the8472 »

batmanthehorse wrote: post #17

Does anyone know of a good way to enable TCP_NODELAY on sockets when you don't have access to the source for that application? I can't find any kernel settings to make it permanent, or commands to change it after the fact. I've been able to disable delayed acks using `quickack 1` in the routing table, but it seems particularly hard to enable TCP_NODELAY from outside the application. I've been having exactly the probl…

opening `/proc//fd/` and setting the socket option may work (not tested)
Post reply on HN