netdev - Re: [PATCH] net: Remove the source address setting in connect() for UDP

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Message-ID: <1DCD31CA-E94F-4127-876F-8DD355E6CF9A@cisco.com>
Date:   Fri, 6 Sep 2019 07:23:43 +0000
From:   "Enke Chen (enkechen)" <enkechen@...co.com>
To:     David Miller <davem@...emloft.net>
CC:     "kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
        "yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xe-linux-external(mailer list)" <xe-linux-external@...co.com>,
        "Enke Chen (enkechen)" <enkechen@...co.com>
Subject: Re: [PATCH] net: Remove the source address setting in connect() for
 UDP

Hi, David:

Yes, I understand the code has been there for a long time.  But the issues are real, and it's really nasty when
You run into them.  As I described in the patch log, there is no backward compatibility Issue for fixing it.

---
There is no backward compatibility issue here as the source address setting
in connect() is not needed anyway.

  - No impact on the source address selection when the source address
    is explicitly specified by "bind()", or by the "IP_PKTINFO" option.

  - In the case that the source address is not explicitly specified,
    the selection of the source address would be more accurate and
    reliable based on the up-to-date routing table.
---

Thanks.  -- Enke

-----Original Message-----
From: <linux-kernel-owner@...r.kernel.org> on behalf of David Miller <davem@...emloft.net>
Date: Friday, September 6, 2019 at 12:14 AM
To: "Enke Chen (enkechen)" <enkechen@...co.com>
Cc: "kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>, "yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "xe-linux-external(mailer list)" <xe-linux-external@...co.com>
Subject: Re: [PATCH] net: Remove the source address setting in connect() for UDP

From: Enke Chen <enkechen@...co.com>
Date: Thu,  5 Sep 2019 19:54:37 -0700

> The connect() system call for a UDP socket is for setting the destination
> address and port. But the current code mistakenly sets the source address
> for the socket as well. Remove the source address setting in connect() for
> UDP in this patch.

Do you have any idea how many decades of precedence this behavior has and
therefore how much you potentially will break userspace?

This boat has sailed a long time ago I'm afraid.