git: 6d20b6de6ae2 - stable/13 - if_epair: delete mbuf tags

The branch stable/13 has been updated by kp:

URL: https://cgit.FreeBSD.org/src/commit/?id=6d20b6de6ae219114049a8fd14e3bd70c10876c0

commit 6d20b6de6ae219114049a8fd14e3bd70c10876c0
Author:     Kristof Provost <kp@FreeBSD.org>
AuthorDate: 2021-10-26 07:57:56 +0000
Commit:     Kristof Provost <kp@FreeBSD.org>
CommitDate: 2021-11-19 05:51:58 +0000

    if_epair: delete mbuf tags
    
    Remove all (non-persistent) tags when we transmit a packet. Real network
    interfaces do not carry any tags either, and leaving tags attached can
    produce unexpected results.
    
    Reviewed by:    bz, glebius
    MFC after:      3 weeks
    Sponsored by:   Rubicon Communications, LLC ("Netgate")
    Differential Revision:  https://reviews.freebsd.org/D32663
    
    (cherry picked from commit 62d2dcafb7f33fe8f47e9d5dd519d665f7af140e)
---
 sys/net/if_epair.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/sys/net/if_epair.c b/sys/net/if_epair.c
index 3cef6c76a2e2..2feefedb3cd9 100644
--- a/sys/net/if_epair.c
+++ b/sys/net/if_epair.c
@@ -195,6 +195,19 @@ struct epair_dpcpu {
 };
 DPCPU_DEFINE(struct epair_dpcpu, epair_dpcpu);
 
+static void
+epair_clear_mbuf(struct mbuf *m)
+{
+	/* Remove any CSUM_SND_TAG as ether_input will barf. */
+	if (m->m_pkthdr.csum_flags & CSUM_SND_TAG) {
+		m_snd_tag_rele(m->m_pkthdr.snd_tag);
+		m->m_pkthdr.snd_tag = NULL;
+		m->m_pkthdr.csum_flags &= ~CSUM_SND_TAG;
+	}
+
+	m_tag_delete_nonpersistent(m);
+}
+
 static void
 epair_dpcpu_init(void)
 {
@@ -434,6 +447,8 @@ epair_start_locked(struct ifnet *ifp)
 		}
 		DPRINTF("packet %s -> %s\n", ifp->if_xname, oifp->if_xname);
 
+		epair_clear_mbuf(m);
+
 		/*
 		 * Add a reference so the interface cannot go while the
 		 * packet is in transit as we rely on rcvif to stay valid.
@@ -555,6 +570,9 @@ epair_transmit_locked(struct ifnet *ifp, struct mbuf *m)
 			(void)epair_add_ifp_for_draining(ifp);
 		return (error);
 	}
+
+	epair_clear_mbuf(m);
+
 	sc = oifp->if_softc;
 	/*
 	 * Add a reference so the interface cannot go while the