Re: 6543fa5a5c47 - main - dumpon: warn if the configured netdump link is down

-----Original Message-----
From: <owner-src-committers@freebsd.org> on behalf of Mitchell Horne <mhorne@FreeBSD.org>
Date: 2022-05-14, Saturday at 06:28
To: <src-committers@FreeBSD.org>, <dev-commits-src-all@FreeBSD.org>, <dev-commits-src-main@FreeBSD.org>
Subject: git: 6543fa5a5c47 - main - dumpon: warn if the configured netdump link is down

    The branch main has been updated by mhorne:

    URL: https://cgit.FreeBSD.org/src/commit/?id=6543fa5a5c47cfbea92586f0994431fc8ba09f6a

    commit 6543fa5a5c47cfbea92586f0994431fc8ba09f6a
    Author:     Mitchell Horne <mhorne@FreeBSD.org>
    AuthorDate: 2022-05-14 13:25:21 +0000
    Commit:     Mitchell Horne <mhorne@FreeBSD.org>
    CommitDate: 2022-05-14 13:27:54 +0000

        dumpon: warn if the configured netdump link is down

        Previously we expected the DIOCSKERNELDUMP ioctl to return ENXIO if the
        interface was down, but it does not actually do this. Grab the link
        status using getifaddrs(3) instead, and downgrade this case from an
        error to a warning; the user might bring the link back up at a later
        time.

Testing whether or not a given link is up sounds like something that should be in libifconfig. If it's there, wouldn't it be better to use that rather than creating check_link_status()? And if it's not there, shouldn't it be?

Thanks,

Ravi (rpokala@)

        Reviewed by:    cem
        MFC after:      1 week
        Differential Revision:  https://reviews.freebsd.org/D35196
    ---
     sbin/dumpon/dumpon.c | 27 +++++++++++++++++++++++----
     1 file changed, 23 insertions(+), 4 deletions(-)

    diff --git a/sbin/dumpon/dumpon.c b/sbin/dumpon/dumpon.c
    index 7d8f81d5eaaf..626350427595 100644
    --- a/sbin/dumpon/dumpon.c
    +++ b/sbin/dumpon/dumpon.c
    @@ -186,6 +186,25 @@ find_gateway(const char *ifname)
     	return (ret);
     }

    +static void
    +check_link_status(const char *ifname)
    +{
    +	struct ifaddrs *ifap, *ifa;
    +
    +	if (getifaddrs(&ifap) != 0)
    +		err(EX_OSERR, "getifaddrs");
    +
    +	for (ifa = ifap; ifa != NULL; ifa = ifa->ifa_next) {
    +		if (strcmp(ifname, ifa->ifa_name) != 0)
    +			continue;
    +		if ((ifa->ifa_flags & IFF_UP) == 0) {
    +			warnx("warning: %s's link is down", ifname);
    +		}
    +		break;
    +	}
    +	freeifaddrs(ifap);
    +}
    +
     static void
     check_size(int fd, const char *fn)
     {
    @@ -659,6 +678,9 @@ main(int argc, char *argv[])
     		else
     			error = errno;
     	}
    +	/* Emit a warning if the user configured a downed interface. */
    +	if (error == 0 && netdump)
    +		check_link_status(kdap->kda_iface);
     	explicit_bzero(kdap->kda_encryptedkey, kdap->kda_encryptedkeysize);
     	free(kdap->kda_encryptedkey);
     	explicit_bzero(kdap, sizeof(*kdap));
    @@ -669,10 +691,7 @@ main(int argc, char *argv[])
     			 * errors, especially as users don't have any great
     			 * discoverability into which NICs support netdump.
     			 */
    -			if (error == ENXIO)
    -				errx(EX_OSERR, "Unable to configure netdump "
    -				    "because the interface's link is down.");
    -			else if (error == ENODEV)
    +			if (error == ENODEV)
     				errx(EX_OSERR, "Unable to configure netdump "
     				    "because the interface driver does not yet "
     				    "support netdump.");