Date: Wed, 03 May 2017 14:00:33 -0700 From: John Baldwin <jhb@freebsd.org> To: Ian Lepore <ian@freebsd.org> Cc: Ryan Stone <rysto32@gmail.com>, Alan Somers <asomers@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r317755 - head/sbin/ifconfig Message-ID: <2536795.sxmMB4gFZB@ralph.baldwin.cx> In-Reply-To: <1493838199.80042.14.camel@freebsd.org> References: <201705031721.v43HL2vS071819@repo.freebsd.org> <CAFMmRNyUXZz==Xdh8fqbw7BqYCHig%2BXAEOj1dxcJ2p0H6_qWeA@mail.gmail.com> <1493838199.80042.14.camel@freebsd.org>
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On Wednesday, May 03, 2017 01:03:19 PM Ian Lepore wrote: > On Wed, 2017-05-03 at 14:07 -0400, Ryan Stone wrote: > > On Wed, May 3, 2017 at 1:39 PM, Ryan Stone <rysto32@gmail.com> wrote: > > > > > > > > > > > > > > On Wed, May 3, 2017 at 1:21 PM, Alan Somers <asomers@freebsd.org> wrote: > > > > > > > > > > > Author: asomers > > > > Date: Wed May 3 17:21:01 2017 > > > > New Revision: 317755 > > > > URL: https://svnweb.freebsd.org/changeset/base/317755 > > > > > > > > Log: > > > > Various Coverity fixes in ifconfig(8) > > > > > > > > * Exit early if kldload(2) fails (1011259). This is the only change that > > > > affects ifconfig's behavior. > > > > > > > > > > > Please revert this ASAP. kldload is expected to fail for a number of > > > benign reasons and this change is likely to prevent any network > > > configuration from being applied to systems, breaking remote access. > > > > > > > > It's been pointed out to me off-list that the situation is not quite as > > dire as I had originally believed. The ifconfig code in question already > > searches to check if the module in question is loaded before calling > > kldload. However, there is at least one driver (mlx4_en) that does not > > follow the "if_" kld module naming convention that this code depends > > on, so this change will make it impossible to apply configuration to > > mlx4_en interfaces. Additionally, it is possible that other drivers use > > the naming convention for their kld file but not for the module declared in > > the C code, in which case this change would also break configuration of > > those interfaces. > > > > jhb@ suggests that ifconfig should only attempt to load a module if the > > interface doesn't already exist, by calling if_nametoindex to check for the > > existence of the interface. That seems to be a reasonable fix for me, but > > in the interest of not breaking users' networking configuration > > (potentially making it impossible to fix a remote machine), I'd recommend > > that the part of the change that checks the return code from kldload() be > > reverted while a fix for this issue is worked on. > > It should be noted that the existing code uses if_nametoindex() > immediately after ifmaybeload() returns, and handles errors > accordingly. I.e., there wasn't really anything wrong with the code as > originally written/structured. Except it's really klunky. The loop searching the module list is a lot more code than ignoring EEXIST errors from kldload. I would structure the code like this: ifindex = if_nametoindex(ifname); if (ifindex == 0) { ifmaybeload(ifname); ifindex = if_nametoindex(ifname); } if (ifindex == 0) { /* existing code */ } Further, I would probably simplify ifmaybeload() to be something like this: static void ifmaybeload(const char *name) { if (noload) return; /* existing code to generate 'ifkind' */ if (kldload(ifkind) == -1) { if (errno != EEXIST) err(...); } } One could argue for ignoring ENOENT errors as well, but Alan's specific use case is one that wanted an explicit kldload error for ENOENT. -- John Baldwin
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