git: 956acdce0505 - main - loopback: Account for packet drops

The branch main has been updated by gallatin:

URL: https://cgit.FreeBSD.org/src/commit/?id=956acdce0505ca8028d287d3b44789c623c8f37e

commit 956acdce0505ca8028d287d3b44789c623c8f37e
Author:     Andrew Gallatin <gallatin@FreeBSD.org>
AuthorDate: 2026-04-14 19:43:28 +0000
Commit:     Andrew Gallatin <gallatin@FreeBSD.org>
CommitDate: 2026-04-14 19:43:28 +0000

    loopback: Account for packet drops
    
    Make loopback packet drops more obvious by reporting them
    in interface stats visable via netstat -ni
    Since loopback uses netisr, packets can be dropped if the
    netisr queue overflows.  These drops are visible via
    netisr -Q, but its not an obvious place to look.
    
    Differential Revision: https://reviews.freebsd.org/D56356
    Reviewed by: glebius, tuexen
    Sponsored by: Netflix
---
 sys/net/if_loop.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/sys/net/if_loop.c b/sys/net/if_loop.c
index 37309260a0d3..2ff265d5d1e7 100644
--- a/sys/net/if_loop.c
+++ b/sys/net/if_loop.c
@@ -350,9 +350,13 @@ if_simloop(struct ifnet *ifp, struct mbuf *m, int af, int hlen)
 		m_freem(m);
 		return (EAFNOSUPPORT);
 	}
-	if_inc_counter(ifp, IFCOUNTER_IPACKETS, 1);
-	if_inc_counter(ifp, IFCOUNTER_IBYTES, m->m_pkthdr.len);
-	netisr_queue(isr, m);	/* mbuf is free'd on failure. */
+	if (netisr_queue(isr, m) == 0) {
+		if_inc_counter(ifp, IFCOUNTER_IPACKETS, 1);
+		if_inc_counter(ifp, IFCOUNTER_IBYTES, m->m_pkthdr.len);
+	} else {
+		/* mbuf is free'd on failure. */
+		if_inc_counter(ifp, IFCOUNTER_IQDROPS, 1);
+	}
 	return (0);
 }