In the next commit it must be possible for the callers of function
tap_push_l2h() to specify which source MAC address should be
added to the ethernet header sent over the tap interface. As a
preparation, we now add a new argument to that function, still
without any logical changes.
Signed-off-by: Jon Maloy
Reviewed-by: David Gibson
---
v3: -Improved comment for src_mac argument, as suggested by Stefano.
v4: -Re-added comment in tap.c and remove redundant argument check
in tap_push_l2()
v5: -Ensured that MAC argument to tap_push_l2h() never is NULL.
v6: -Clarification of comment about ARP lookup
v12: - Minor updates after feedback from Stefano
---
tap.c | 16 +++++++++-------
tap.h | 3 ++-
tcp.c | 6 ++++--
3 files changed, 15 insertions(+), 10 deletions(-)
diff --git a/tap.c b/tap.c
index 250a0f6..84266d0 100644
--- a/tap.c
+++ b/tap.c
@@ -171,17 +171,19 @@ const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
* tap_push_l2h() - Build an L2 header for an inbound packet
* @c: Execution context
* @buf: Buffer address at which to generate header
+ * @src_mac: MAC address to be used as source for message
* @proto: Ethernet protocol number for L3
*
* Return: pointer at which to write the packet's payload
*/
-void *tap_push_l2h(const struct ctx *c, void *buf, uint16_t proto)
+void *tap_push_l2h(const struct ctx *c, void *buf,
+ const void *src_mac, uint16_t proto)
{
struct ethhdr *eh = (struct ethhdr *)buf;
- /* TODO: ARP table lookup */
+ /* TODO: ARP lookup on tap side */
memcpy(eh->h_dest, c->guest_mac, ETH_ALEN);
- memcpy(eh->h_source, c->our_tap_mac, ETH_ALEN);
+ memcpy(eh->h_source, src_mac, ETH_ALEN);
eh->h_proto = ntohs(proto);
return eh + 1;
}
@@ -261,7 +263,7 @@ void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
{
size_t l4len = dlen + sizeof(struct udphdr);
char buf[USHRT_MAX];
- struct iphdr *ip4h = tap_push_l2h(c, buf, ETH_P_IP);
+ struct iphdr *ip4h = tap_push_l2h(c, buf, c->our_tap_mac, ETH_P_IP);
struct udphdr *uh = tap_push_ip4h(ip4h, src, dst, l4len, IPPROTO_UDP);
char *data = tap_push_uh4(uh, src, sport, dst, dport, in, dlen);
@@ -281,7 +283,7 @@ void tap_icmp4_send(const struct ctx *c, struct in_addr src, struct in_addr dst,
const void *in, size_t l4len)
{
char buf[USHRT_MAX];
- struct iphdr *ip4h = tap_push_l2h(c, buf, ETH_P_IP);
+ struct iphdr *ip4h = tap_push_l2h(c, buf, c->our_tap_mac, ETH_P_IP);
struct icmphdr *icmp4h = tap_push_ip4h(ip4h, src, dst,
l4len, IPPROTO_ICMP);
@@ -367,7 +369,7 @@ void tap_udp6_send(const struct ctx *c,
{
size_t l4len = dlen + sizeof(struct udphdr);
char buf[USHRT_MAX];
- struct ipv6hdr *ip6h = tap_push_l2h(c, buf, ETH_P_IPV6);
+ struct ipv6hdr *ip6h = tap_push_l2h(c, buf, c->our_tap_mac, ETH_P_IPV6);
struct udphdr *uh = tap_push_ip6h(ip6h, src, dst,
l4len, IPPROTO_UDP, flow);
char *data = tap_push_uh6(uh, src, sport, dst, dport, in, dlen);
@@ -389,7 +391,7 @@ void tap_icmp6_send(const struct ctx *c,
const void *in, size_t l4len)
{
char buf[USHRT_MAX];
- struct ipv6hdr *ip6h = tap_push_l2h(c, buf, ETH_P_IPV6);
+ struct ipv6hdr *ip6h = tap_push_l2h(c, buf, c->our_tap_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 21db4d2..02f7761 100644
--- a/tap.h
+++ b/tap.h
@@ -70,7 +70,8 @@ static inline void tap_hdr_update(struct tap_hdr *thdr, size_t l2len)
}
unsigned long tap_l2_max_len(const struct ctx *c);
-void *tap_push_l2h(const struct ctx *c, void *buf, uint16_t proto);
+void *tap_push_l2h(const struct ctx *c, void *buf,
+ const void *src_mac, uint16_t proto);
void *tap_push_ip4h(struct iphdr *ip4h, struct in_addr src,
struct in_addr dst, size_t l4len, uint8_t proto);
void *tap_push_uh4(struct udphdr *uh, struct in_addr src, in_port_t sport,
diff --git a/tcp.c b/tcp.c
index 06b07f8..79d2efe 100644
--- a/tcp.c
+++ b/tcp.c
@@ -1979,7 +1979,8 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
return;
if (af == AF_INET) {
- struct iphdr *ip4h = tap_push_l2h(c, buf, ETH_P_IP);
+ struct iphdr *ip4h = tap_push_l2h(c, buf, c->our_tap_mac,
+ ETH_P_IP);
const struct in_addr *rst_src = daddr;
const struct in_addr *rst_dst = saddr;
@@ -1989,7 +1990,8 @@ static void tcp_rst_no_conn(const struct ctx *c, int af,
*rst_src, *rst_dst);
} else {
- struct ipv6hdr *ip6h = tap_push_l2h(c, buf, ETH_P_IPV6);
+ struct ipv6hdr *ip6h = tap_push_l2h(c, buf, c->our_tap_mac,
+ ETH_P_IPV6);
const struct in6_addr *rst_src = daddr;
const struct in6_addr *rst_dst = saddr;
--
2.50.1