From 1d126e9b947405fe9dea89ef564d42e89fc6e814 Mon Sep 17 00:00:00 2001
From: Kristof Provost <kp@FreeBSD.org>
Date: Sun, 12 Apr 2020 16:09:21 +0000
Subject: [PATCH] carp: Widen epoch coverage

Fix panics related to calling code which expects to be running inside
the NET_EPOCH from outside that epoch.

This leads to panics (with INVARIANTS) such as this one:

    panic: Assertion in_epoch(net_epoch_preempt) failed at /usr/src/sys/netinet/if_ether.c:373
    cpuid = 7
    time = 1586095719
    KDB: stack backtrace:
    db_trace_self_wrapper() at db_trace_self_wrapper+0x2b/frame 0xfffffe0090819700
    vpanic() at vpanic+0x182/frame 0xfffffe0090819750
    panic() at panic+0x43/frame 0xfffffe00908197b0
    arprequest_internal() at arprequest_internal+0x59e/frame 0xfffffe00908198c0
    arp_announce_ifaddr() at arp_announce_ifaddr+0x20/frame 0xfffffe00908198e0
    carp_master_down_locked() at carp_master_down_locked+0x10d/frame 0xfffffe0090819910
    carp_master_down() at carp_master_down+0x79/frame 0xfffffe0090819940
    softclock_call_cc() at softclock_call_cc+0x13f/frame 0xfffffe00908199f0
    softclock() at softclock+0x7c/frame 0xfffffe0090819a20
    ithread_loop() at ithread_loop+0x279/frame 0xfffffe0090819ab0
    fork_exit() at fork_exit+0x80/frame 0xfffffe0090819af0
    fork_trampoline() at fork_trampoline+0xe/frame 0xfffffe0090819af0
    --- trap 0, rip = 0, rsp = 0, rbp = 0 ---

Widen the NET_EPOCH to cover the relevant (callback / task) code.

Differential Revision:	https://reviews.freebsd.org/D24302
---
 sys/netinet/ip_carp.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/sys/netinet/ip_carp.c b/sys/netinet/ip_carp.c
index 9d3c51a066b..6b6ef67270b 100644
--- a/sys/netinet/ip_carp.c
+++ b/sys/netinet/ip_carp.c
@@ -817,7 +817,9 @@ static void
 carp_send_ad_all(void *ctx __unused, int pending __unused)
 {
 	struct carp_softc *sc;
+	struct epoch_tracker et;
 
+	NET_EPOCH_ENTER(et);
 	mtx_lock(&carp_mtx);
 	LIST_FOREACH(sc, &carp_list, sc_next)
 		if (sc->sc_state == MASTER) {
@@ -828,6 +830,7 @@ carp_send_ad_all(void *ctx __unused, int pending __unused)
 			CARP_UNLOCK(sc);
 		}
 	mtx_unlock(&carp_mtx);
+	NET_EPOCH_EXIT(et);
 }
 
 /* Send a periodic advertisement, executed in callout context. */
@@ -835,12 +838,15 @@ static void
 carp_send_ad(void *v)
 {
 	struct carp_softc *sc = v;
+	struct epoch_tracker et;
 
+	NET_EPOCH_ENTER(et);
 	CARP_LOCK_ASSERT(sc);
 	CURVNET_SET(sc->sc_carpdev->if_vnet);
 	carp_send_ad_locked(sc);
 	CURVNET_RESTORE();
 	CARP_UNLOCK(sc);
+	NET_EPOCH_EXIT(et);
 }
 
 static void
@@ -907,12 +913,12 @@ carp_send_ad_locked(struct carp_softc *sc)
 {
 	struct carp_header ch;
 	struct timeval tv;
-	struct epoch_tracker et;
 	struct ifaddr *ifa;
 	struct carp_header *ch_ptr;
 	struct mbuf *m;
 	int len, advskew;
 
+	NET_EPOCH_ASSERT();
 	CARP_LOCK_ASSERT(sc);
 
 	advskew = DEMOTE_ADVSKEW(sc);
@@ -976,10 +982,8 @@ carp_send_ad_locked(struct carp_softc *sc)
 
 		CARPSTATS_INC(carps_opackets);
 
-		NET_EPOCH_ENTER(et);
 		carp_send_ad_error(sc, ip_output(m, NULL, NULL, IP_RAWOUTPUT,
 		    &sc->sc_carpdev->if_carp->cif_imo, NULL));
-		NET_EPOCH_EXIT(et);
 	}
 #endif /* INET */
 #ifdef INET6
@@ -1037,10 +1041,8 @@ carp_send_ad_locked(struct carp_softc *sc)
 
 		CARPSTATS_INC(carps_opackets6);
 
-		NET_EPOCH_ENTER(et);
 		carp_send_ad_error(sc, ip6_output(m, NULL, NULL, 0,
 		    &sc->sc_carpdev->if_carp->cif_im6o, NULL, NULL));
-		NET_EPOCH_EXIT(et);
 	}
 #endif /* INET6 */
 
@@ -1130,6 +1132,8 @@ carp_send_arp(struct carp_softc *sc)
 	struct ifaddr *ifa;
 	struct in_addr addr;
 
+	NET_EPOCH_ASSERT();
+
 	CARP_FOREACH_IFA(sc, ifa) {
 		if (ifa->ifa_addr->sa_family != AF_INET)
 			continue;
@@ -1258,7 +1262,9 @@ static void
 carp_master_down(void *v)
 {
 	struct carp_softc *sc = v;
+	struct epoch_tracker et;
 
+	NET_EPOCH_ENTER(et);
 	CARP_LOCK_ASSERT(sc);
 
 	CURVNET_SET(sc->sc_carpdev->if_vnet);
@@ -1268,12 +1274,14 @@ carp_master_down(void *v)
 	CURVNET_RESTORE();
 
 	CARP_UNLOCK(sc);
+	NET_EPOCH_EXIT(et);
 }
 
 static void
 carp_master_down_locked(struct carp_softc *sc, const char *reason)
 {
 
+	NET_EPOCH_ASSERT();
 	CARP_LOCK_ASSERT(sc);
 
 	switch (sc->sc_state) {
-- 
2.45.0