hsr: Fix supervision frame sending on HSRv0

On HSRv0, no supervision frames were sent. The supervison frames were
generated successfully, but failed the check for a sufficiently long mac
header, i.e., at least sizeof(struct hsr_ethhdr), in hsr_fill_frame_info()
because the mac header only contained the ethernet header.

Fix this by including the HSR header in the mac header when generating HSR
supervision frames. Note that the mac header now also includes the TLV
fields. This matches how we set the headers on rx and also the size of
struct hsrv0_ethhdr_sp.

Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Closes: https://lore.kernel.org/netdev/aMONxDXkzBZZRfE5@fedora/
Fixes: 9cfb5e7 ("net: hsr: fix hsr_init_sk() vs network/transport headers.")
Signed-off-by: Felix Maurer <fmaurer@redhat.com>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/4354114fea9a642fe71f49aeeb6c6159d1d61840.1762876095.git.fmaurer@redhat.com
Tested-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: fmaurer-rh

net/hsr/hsr_device.c

@@ -320,6 +320,9 @@ static void send_hsr_supervision_frame(struct hsr_port *port,
 	}
 
 	hsr_stag = skb_put(skb, sizeof(struct hsr_sup_tag));
+	skb_set_network_header(skb, ETH_HLEN + HSR_HLEN);
+	skb_reset_mac_len(skb);
+
 	set_hsr_stag_path(hsr_stag, (hsr->prot_version ? 0x0 : 0xf));
 	set_hsr_stag_HSR_ver(hsr_stag, hsr->prot_version);