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From: Andrea Claudi <aclaudi@redhat.com>
Date: Tue, 28 Sep 2021 11:46:43 +0200
Subject: [PATCH] lib: bpf_legacy: fix bpffs mount when /sys/fs/bpf exists
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1995082
Upstream Status: iproute2.git commit 2f5825cb

commit 2f5825cb38028a14961a79844a069be4e3057eca
Author: Andrea Claudi <aclaudi@redhat.com>
Date:   Tue Sep 21 11:33:24 2021 +0200

    lib: bpf_legacy: fix bpffs mount when /sys/fs/bpf exists

    bpf selftests using iproute2 fails with:

    $ ip link set dev veth0 xdp object ../bpf/xdp_dummy.o section xdp_dummy
    Continuing without mounted eBPF fs. Too old kernel?
    mkdir (null)/globals failed: No such file or directory
    Unable to load program

    This happens when the /sys/fs/bpf directory exists. In this case, mkdir
    in bpf_mnt_check_target() fails with errno == EEXIST, and the function
    returns -1. Thus bpf_get_work_dir() does not call bpf_mnt_fs() and the
    bpffs is not mounted.

    Fix this in bpf_mnt_check_target(), returning 0 when the mountpoint
    exists.

    Fixes: d4fcdbbec9df ("lib/bpf: Fix and simplify bpf_mnt_check_target()")
    Reported-by: Mingyu Shi <mshi@redhat.com>
    Reported-by: Jiri Benc <jbenc@redhat.com>
    Suggested-by: Jiri Benc <jbenc@redhat.com>
    Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
    Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
    Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/bpf_legacy.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/bpf_legacy.c b/lib/bpf_legacy.c
index 7ec9ce9d..f9dfad6e 100644
--- a/lib/bpf_legacy.c
+++ b/lib/bpf_legacy.c
@@ -513,9 +513,12 @@ static int bpf_mnt_check_target(const char *target)
 	int ret;
 
 	ret = mkdir(target, S_IRWXU);
-	if (ret && errno != EEXIST)
+	if (ret) {
+		if (errno == EEXIST)
+			return 0;
 		fprintf(stderr, "mkdir %s failed: %s\n", target,
 			strerror(errno));
+	}
 
 	return ret;
 }
-- 
2.31.1