On Tue, Sep 09, 2025 at 09:59:19PM -0400, Jon Maloy wrote: > Even ICMP needs to be updated to use the external MAC address instead > of just the own tap address when applicable. We do that here. > > Signed-off-by: Jon Maloy Reviewed-by: David Gibson > > --- > v3: - Adapted to the move of external MAC address from struct flowside > to struct flow_common > v4: - Adapted to name changes in previous commits in this series > v5: - Added conditional lookup in ARP/NDP if the flow's tap_omac is > undefined > v6: - Looking up MAC of ICMP generating node in udp_send_tap_icmp4/6() > when available, instead trusting the contents of flow->tap_omac. > --- > icmp.c | 8 ++++++-- > ndp.c | 2 +- > tap.c | 10 ++++++---- > tap.h | 4 ++-- > udp.c | 12 ++++++++++-- > 5 files changed, 25 insertions(+), 11 deletions(-) > > diff --git a/icmp.c b/icmp.c > index 6dffafb..1d99632 100644 > --- a/icmp.c > +++ b/icmp.c > @@ -125,17 +125,21 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref) > flow_dbg(pingf, "echo reply to tap, ID: %"PRIu16", seq: %"PRIu16, > ini->eport, seq); > > + /* Try to find true MAC address in ARP/NDP table if needed */ > + if (MAC_IS_ZERO(pingf->f.tap_omac)) > + fwd_neigh_mac_get(c, &ini->oaddr, pingf->f.tap_omac); > + > if (pingf->f.type == FLOW_PING4) { > const struct in_addr *saddr = inany_v4(&ini->oaddr); > const struct in_addr *daddr = inany_v4(&ini->eaddr); > > ASSERT(saddr && daddr); /* Must have IPv4 addresses */ > - tap_icmp4_send(c, *saddr, *daddr, buf, n); > + tap_icmp4_send(c, *saddr, *daddr, buf, pingf->f.tap_omac, n); > } else if (pingf->f.type == FLOW_PING6) { > const struct in6_addr *saddr = &ini->oaddr.a6; > const struct in6_addr *daddr = &ini->eaddr.a6; > > - tap_icmp6_send(c, saddr, daddr, buf, n); > + tap_icmp6_send(c, saddr, daddr, buf, pingf->f.tap_omac, n); > } > return; > > diff --git a/ndp.c b/ndp.c > index 944371c..1e9d0f4 100644 > --- a/ndp.c > +++ b/ndp.c > @@ -184,7 +184,7 @@ static void ndp_send(const struct ctx *c, const struct in6_addr *dst, > { > const struct in6_addr *src = &c->ip6.our_tap_ll; > > - tap_icmp6_send(c, src, dst, buf, l4len); > + tap_icmp6_send(c, src, dst, buf, c->our_tap_mac, l4len); > } > > /** > diff --git a/tap.c b/tap.c > index a390be8..8b10e14 100644 > --- a/tap.c > +++ b/tap.c > @@ -277,13 +277,14 @@ void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport, > * @src: IPv4 source address > * @dst: IPv4 destination address > * @in: ICMP packet, including ICMP header > + * @src_mac: MAC address to be used as source for message > * @l4len: ICMP packet length, including ICMP header > */ > void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst, > - const void *in, size_t l4len) > + const void *in, const void *src_mac, size_t l4len) > { > char buf[USHRT_MAX]; > - struct iphdr *ip4h = tap_push_l2h(c, buf, c->our_tap_mac, ETH_P_IP); > + struct iphdr *ip4h = tap_push_l2h(c, buf, src_mac, ETH_P_IP); > struct icmphdr *icmp4h = tap_push_ip4h(ip4h, src, dst, > l4len, IPPROTO_ICMP); > > @@ -384,14 +385,15 @@ void tap_udp6_send(const struct ctx *c, > * @src: IPv6 source address > * @dst: IPv6 destination address > * @in: ICMP packet, including ICMP header > + * @src_mac: MAC address to be used as source for message > * @l4len: ICMP packet length, including ICMP header > */ > void tap_icmp6_send(const struct ctx *c, > const struct in6_addr *src, const struct in6_addr *dst, > - const void *in, size_t l4len) > + const void *in, const void *src_mac, size_t l4len) > { > char buf[USHRT_MAX]; > - struct ipv6hdr *ip6h = tap_push_l2h(c, buf, c->our_tap_mac, ETH_P_IPV6); > + struct ipv6hdr *ip6h = tap_push_l2h(c, buf, src_mac, ETH_P_IPV6); > struct icmp6hdr *icmp6h = tap_push_ip6h(ip6h, src, dst, l4len, > IPPROTO_ICMPV6, 0); > > diff --git a/tap.h b/tap.h > index 02f7761..1864173 100644 > --- a/tap.h > +++ b/tap.h > @@ -91,7 +91,7 @@ void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport, > struct in_addr dst, in_port_t dport, > const void *in, size_t dlen); > void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst, > - const void *in, size_t l4len); > + const void *in, const void *src_mac, size_t l4len); > const struct in6_addr *tap_ip6_daddr(const struct ctx *c, > const struct in6_addr *src); > void *tap_push_ip6h(struct ipv6hdr *ip6h, > @@ -103,7 +103,7 @@ void tap_udp6_send(const struct ctx *c, > uint32_t flow, void *in, size_t dlen); > void tap_icmp6_send(const struct ctx *c, > const struct in6_addr *src, const struct in6_addr *dst, > - const void *in, size_t l4len); > + const void *in, const void *src_mac, size_t l4len); > void tap_send_single(const struct ctx *c, const void *data, size_t l2len); > size_t tap_send_frames(const struct ctx *c, const struct iovec *iov, > size_t bufs_per_frame, size_t nframes); > diff --git a/udp.c b/udp.c > index eb57f05..ff15e37 100644 > --- a/udp.c > +++ b/udp.c > @@ -400,6 +400,8 @@ static void udp_send_tap_icmp4(const struct ctx *c, > struct in_addr eaddr = toside->eaddr.v4mapped.a4; > in_port_t eport = toside->eport; > in_port_t oport = toside->oport; > + union inany_addr saddr_any; > + uint8_t tap_omac[ETH_ALEN]; > struct { > struct icmphdr icmp4h; > struct iphdr ip4h; > @@ -421,7 +423,10 @@ static void udp_send_tap_icmp4(const struct ctx *c, > tap_push_uh4(&msg.uh, eaddr, eport, oaddr, oport, in, dlen); > memcpy(&msg.data, in, dlen); > > - tap_icmp4_send(c, saddr, eaddr, &msg, msglen); > + /* Try to obtain the MAC address of the generating node */ > + saddr_any = inany_from_v4(saddr); > + fwd_neigh_mac_get(c, &saddr_any, tap_omac); > + tap_icmp4_send(c, saddr, eaddr, &msg, tap_omac, msglen); > } > > > @@ -445,6 +450,7 @@ static void udp_send_tap_icmp6(const struct ctx *c, > const struct in6_addr *eaddr = &toside->eaddr.a6; > in_port_t eport = toside->eport; > in_port_t oport = toside->oport; > + uint8_t tap_omac[ETH_ALEN]; > struct { > struct icmp6_hdr icmp6h; > struct ipv6hdr ip6h; > @@ -466,7 +472,9 @@ static void udp_send_tap_icmp6(const struct ctx *c, > tap_push_uh6(&msg.uh, eaddr, eport, oaddr, oport, in, dlen); > memcpy(&msg.data, in, dlen); > > - tap_icmp6_send(c, saddr, eaddr, &msg, msglen); > + /* Try to obtain the MAC address of the generating node */ > + fwd_neigh_mac_get(c, (union inany_addr *) saddr, tap_omac); > + tap_icmp6_send(c, saddr, eaddr, &msg, tap_omac, msglen); > } > > /** > -- > 2.50.1 > -- David Gibson (he or they) | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you, not the other way | around. http://www.ozlabs.org/~dgibson