git: a9bfd080d09a - main - if_epair: do not transmit packets that exceed the interface MTU

The branch main has been updated by kp:

URL: https://cgit.FreeBSD.org/src/commit/?id=a9bfd080d09a915055af51103defb5c38b94a236

commit a9bfd080d09a915055af51103defb5c38b94a236
Author:     Kristof Provost <kp@FreeBSD.org>
AuthorDate: 2023-06-02 14:37:09 +0000
Commit:     Kristof Provost <kp@FreeBSD.org>
CommitDate: 2023-06-06 08:00:48 +0000

    if_epair: do not transmit packets that exceed the interface MTU
    
    While if_epair has no issues doing this we should drop those packets
    anyway, because it improves the fidelity of the automated tests.
    
    Sponsored by:   Rubicon Communications, LLC ("Netgate")
    Differential Revision:  https://reviews.freebsd.org/D40397
---
 sys/net/if_epair.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/sys/net/if_epair.c b/sys/net/if_epair.c
index aee5a76a046b..56bfdfbd610f 100644
--- a/sys/net/if_epair.c
+++ b/sys/net/if_epair.c
@@ -336,6 +336,17 @@ epair_transmit(struct ifnet *ifp, struct mbuf *m)
 		return (0);
 	M_ASSERTPKTHDR(m);
 
+	/*
+	 * We could just transmit this, but it makes testing easier if we're a
+	 * little bit more like real hardware.
+	 * Allow just that little bit extra for ethernet (and vlan) headers.
+	 */
+	if (m->m_pkthdr.len > (ifp->if_mtu + sizeof(struct ether_vlan_header))) {
+		m_freem(m);
+		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
+		return (E2BIG);
+	}
+
 	/*
 	 * We are not going to use the interface en/dequeue mechanism
 	 * on the TX side. We are called from ether_output_frame()