Put checksum flags in bpf_hdr to use them in userland dhcpleased.

Thus, dhcpleased accept non-calculated checksums which were verified by
hardware/hypervisor.

With tweaks from dlg@

ok bluhm@
mkay tobhe@

5 files changed, 24 insertions, 15 deletions

diff --git a/sbin/dhcpleased/dhcpleased.h b/sbin/dhcpleased/dhcpleased.h
index 80fe9dcf5fe..41749fc5031 100644
--- a/sbin/dhcpleased/dhcpleased.h
+++ b/sbin/dhcpleased/dhcpleased.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dhcpleased.h,v 1.15 2023/11/25 12:00:39 florian Exp $	*/
+/*	$OpenBSD: dhcpleased.h,v 1.16 2024/01/26 21:14:08 jan Exp $	*/
 
 /*
  * Copyright (c) 2017, 2021 Florian Obser <florian@openbsd.org>
@@ -287,7 +287,7 @@ struct imsg_propose_rdns {
 struct imsg_dhcp {
 	uint32_t		if_index;
 	ssize_t			len;
-	uint8_t			ether_align[2];
+	uint16_t		csumflags;
 	uint8_t			packet[1500];
 };
 
diff --git a/sbin/dhcpleased/engine.c b/sbin/dhcpleased/engine.c
index cc6610f2d47..6d371a5a112 100644
--- a/sbin/dhcpleased/engine.c
+++ b/sbin/dhcpleased/engine.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: engine.c,v 1.41 2023/12/14 09:58:37 claudio Exp $	*/
+/*	$OpenBSD: engine.c,v 1.42 2024/01/26 21:14:08 jan Exp $	*/
 
 /*
  * Copyright (c) 2017, 2021 Florian Obser <florian@openbsd.org>
@@ -24,6 +24,7 @@
 #include <sys/socket.h>
 #include <sys/syslog.h>
 #include <sys/uio.h>
+#include <sys/mbuf.h>
 
 #include <net/if.h>
 #include <net/route.h>
@@ -788,7 +789,8 @@ parse_dhcp(struct dhcpleased_iface *iface, struct imsg_dhcp *dhcp)
 	if (rem < (size_t)ip->ip_hl << 2)
 		goto too_short;
 
-	if (wrapsum(checksum((uint8_t *)ip, ip->ip_hl << 2, 0)) != 0) {
+	if ((dhcp->csumflags & M_IPV4_CSUM_IN_OK) == 0 &&
+	    wrapsum(checksum((uint8_t *)ip, ip->ip_hl << 2, 0)) != 0) {
 		log_warnx("%s: bad IP checksum", __func__);
 		return;
 	}
@@ -834,16 +836,19 @@ parse_dhcp(struct dhcpleased_iface *iface, struct imsg_dhcp *dhcp)
 	p += sizeof(*udp);
 	rem -= sizeof(*udp);
 
-	usum = udp->uh_sum;
-	udp->uh_sum = 0;
+	if ((dhcp->csumflags & M_UDP_CSUM_IN_OK) == 0) {
+		usum = udp->uh_sum;
+		udp->uh_sum = 0;
 
-	sum = wrapsum(checksum((uint8_t *)udp, sizeof(*udp), checksum(p, rem,
-	    checksum((uint8_t *)&ip->ip_src, 2 * sizeof(ip->ip_src),
-	    IPPROTO_UDP + ntohs(udp->uh_ulen)))));
+		sum = wrapsum(checksum((uint8_t *)udp, sizeof(*udp),
+		    checksum(p, rem,
+		    checksum((uint8_t *)&ip->ip_src, 2 * sizeof(ip->ip_src),
+		    IPPROTO_UDP + ntohs(udp->uh_ulen)))));
 
-	if (usum != 0 && usum != sum) {
-		log_warnx("%s: bad UDP checksum", __func__);
-		return;
+		if (usum != 0 && usum != sum) {
+			log_warnx("%s: bad UDP checksum", __func__);
+			return;
+		}
 	}
 
 	if (log_getverbose() > 1) {
diff --git a/sbin/dhcpleased/frontend.c b/sbin/dhcpleased/frontend.c
index 74335b88e63..b80b8081e03 100644
--- a/sbin/dhcpleased/frontend.c
+++ b/sbin/dhcpleased/frontend.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: frontend.c,v 1.32 2023/12/14 09:58:37 claudio Exp $	*/
+/*	$OpenBSD: frontend.c,v 1.33 2024/01/26 21:14:08 jan Exp $	*/
 
 /*
  * Copyright (c) 2017, 2021 Florian Obser <florian@openbsd.org>
@@ -890,6 +890,7 @@ bpf_receive(int fd, short events, void *arg)
 		}
 		memcpy(&imsg_dhcp.packet, p + hdr->bh_hdrlen, hdr->bh_caplen);
 		imsg_dhcp.len = hdr->bh_caplen;
+		imsg_dhcp.csumflags = hdr->bh_csumflags;
 		frontend_imsg_compose_engine(IMSG_DHCP, 0, 0, &imsg_dhcp,
 		    sizeof(imsg_dhcp));
  cont:
diff --git a/sys/net/bpf.c b/sys/net/bpf.c
index b05c5177f6e..51a1ed66ff4 100644
--- a/sys/net/bpf.c
+++ b/sys/net/bpf.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bpf.c,v 1.221 2023/03/09 05:56:58 dlg Exp $	*/
+/*	$OpenBSD: bpf.c,v 1.222 2024/01/26 21:14:08 jan Exp $	*/
 /*	$NetBSD: bpf.c,v 1.33 1997/02/21 23:59:35 thorpej Exp $	*/
 
 /*
@@ -1397,6 +1397,8 @@ _bpf_mtap(caddr_t arg, const struct mbuf *mp, const struct mbuf *m,
 					if (ISSET(mp->m_pkthdr.csum_flags,
 					    M_FLOWID))
 						SET(tbh.bh_flags, BPF_F_FLOWID);
+					tbh.bh_csumflags =
+					    mp->m_pkthdr.csum_flags;
 
 					m_microtime(mp, &tv);
 				} else
diff --git a/sys/net/bpf.h b/sys/net/bpf.h
index 9ce4dcd63a4..ab64061fb97 100644
--- a/sys/net/bpf.h
+++ b/sys/net/bpf.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: bpf.h,v 1.71 2023/03/09 05:56:58 dlg Exp $	*/
+/*	$OpenBSD: bpf.h,v 1.72 2024/01/26 21:14:08 jan Exp $	*/
 /*	$NetBSD: bpf.h,v 1.15 1996/12/13 07:57:33 mikel Exp $	*/
 
 /*
@@ -161,6 +161,7 @@ struct bpf_hdr {
 #define BPF_F_DIR_IN		(BPF_DIRECTION_IN << BPF_F_DIR_SHIFT)
 #define BPF_F_DIR_OUT		(BPF_DIRECTION_OUT << BPF_F_DIR_SHIFT)
 	u_int8_t	bh_drops;
+	u_int16_t	bh_csumflags;	/* checksum flags */
 };
 
 #ifdef _KERNEL