The IPv4 and IPv6 paths in tap_ip_send() have very little in common, and
it turns out that every caller (statically) knows if it is using IPv4 or
IPv6. So split into separate tap_ip4_send() and tap_ip6_send() functions.
Use a new tap_l2_hdr() function for the very small common part.
While we're there, make some minor cleanups:
- We were double writing some fields in the IPv6 header, so that it
temporary matched the pseudo-header for checksum calculation. With
recent checksum reworks, this isn't neccessary any more.
- We don't use any IPv4 header options, so use some sizeof() constructs
instead of some open coded values for header length.
- The comment used to say that the flow label was for TCP over IPv6, but
in fact the only thing we used it for was DHCPv6 over UDP traffic
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
dhcpv6.c | 6 +-
icmp.c | 10 +---
tap.c | 177 +++++++++++++++++++++++++++++--------------------------
tap.h | 6 +-
4 files changed, 103 insertions(+), 96 deletions(-)
diff --git a/dhcpv6.c b/dhcpv6.c
index e7640ce..7829968 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -531,8 +531,8 @@ int dhcpv6(struct ctx *c, const struct pool *p,
resp_not_on_link.hdr.xid = mh->xid;
- tap_ip_send(c, src, IPPROTO_UDP,
- (char *)&resp_not_on_link, n, mh->xid);
+ tap_ip6_send(c, src, IPPROTO_UDP,
+ (char *)&resp_not_on_link, n, mh->xid);
return 1;
}
@@ -580,7 +580,7 @@ int dhcpv6(struct ctx *c, const struct pool *p,
resp.hdr.xid = mh->xid;
- tap_ip_send(c, src, IPPROTO_UDP, (char *)&resp, n, mh->xid);
+ tap_ip6_send(c, src, IPPROTO_UDP, (char *)&resp, n, mh->xid);
c->ip6.addr_seen = c->ip6.addr;
return 1;
diff --git a/icmp.c b/icmp.c
index 21ea2d7..61c2d90 100644
--- a/icmp.c
+++ b/icmp.c
@@ -69,10 +69,6 @@ static uint8_t icmp_act[IP_VERSIONS][DIV_ROUND_UP(ICMP_NUM_IDS, 8)];
void icmp_sock_handler(const struct ctx *c, union epoll_ref ref,
uint32_t events, const struct timespec *now)
{
- struct in6_addr a6 = { .s6_addr = { 0, 0, 0, 0,
- 0, 0, 0, 0,
- 0, 0, 0xff, 0xff,
- 0, 0, 0, 0 } };
union icmp_epoll_ref *iref = &ref.r.p.icmp;
struct sockaddr_storage sr;
socklen_t sl = sizeof(sr);
@@ -109,7 +105,7 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref,
icmp_id_map[V6][id].seq = seq;
}
- tap_ip_send(c, &sr6->sin6_addr, IPPROTO_ICMPV6, buf, n, 0);
+ tap_ip6_send(c, &sr6->sin6_addr, IPPROTO_ICMPV6, buf, n, 0);
} else {
struct sockaddr_in *sr4 = (struct sockaddr_in *)&sr;
struct icmphdr *ih = (struct icmphdr *)buf;
@@ -127,9 +123,7 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref,
icmp_id_map[V4][id].seq = seq;
}
- memcpy(&a6.s6_addr[12], &sr4->sin_addr, sizeof(sr4->sin_addr));
-
- tap_ip_send(c, &a6, IPPROTO_ICMP, buf, n, 0);
+ tap_ip4_send(c, sr4->sin_addr.s_addr, IPPROTO_ICMP, buf, n);
}
}
diff --git a/tap.c b/tap.c
index 07592dd..0e8c99b 100644
--- a/tap.c
+++ b/tap.c
@@ -113,100 +113,111 @@ const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
}
/**
- * tap_ip_send() - Send IP packet, with L2 headers, calculating L3/L4 checksums
+ * tap_push_l2h() - Build an L2 header for an inbound packet
* @c: Execution context
- * @src: IPv6 source address, IPv4-mapped for IPv4 sources
- * @proto: L4 protocol number
- * @in: Payload
- * @len: L4 payload length
- * @flow: Flow label for TCP over IPv6
+ * @buf: Buffer address at which to generate header
+ * @proto: Ethernet protocol number for L3
+ *
+ * Return: pointer at which to write the packet's payload
*/
-void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
- const char *in, size_t len, uint32_t flow)
+static void *tap_push_l2h(const struct ctx *c, void *buf, uint16_t proto)
{
- char buf[USHRT_MAX];
- struct ethhdr *eh;
-
- eh = (struct ethhdr *)buf;
+ struct ethhdr *eh = (struct ethhdr *)buf;
/* TODO: ARP table lookup */
memcpy(eh->h_dest, c->mac_guest, ETH_ALEN);
memcpy(eh->h_source, c->mac, ETH_ALEN);
+ eh->h_proto = ntohs(proto);
+ return eh + 1;
+}
- if (IN6_IS_ADDR_V4MAPPED(src)) {
- struct iphdr *iph = (struct iphdr *)(eh + 1);
- char *data = (char *)(iph + 1);
-
- eh->h_proto = ntohs(ETH_P_IP);
-
- iph->version = 4;
- iph->ihl = 5;
- iph->tos = 0;
- iph->tot_len = htons(len + 20);
- iph->id = 0;
- iph->frag_off = 0;
- iph->ttl = 255;
- iph->protocol = proto;
- iph->daddr = tap_ip4_daddr(c);
- memcpy(&iph->saddr, &src->s6_addr[12], 4);
-
- csum_ip4_header(iph);
-
- memcpy(data, in, len);
-
- if (iph->protocol == IPPROTO_UDP) {
- struct udphdr *uh = (struct udphdr *)(iph + 1);
-
- csum_udp4(uh, iph->saddr, iph->daddr, uh + 1, len - sizeof(*uh));
- } else if (iph->protocol == IPPROTO_ICMP) {
- struct icmphdr *ih = (struct icmphdr *)(iph + 1);
- csum_icmp4(ih, ih + 1, len - sizeof(*ih));
- }
-
- if (tap_send(c, buf, len + sizeof(*iph) + sizeof(*eh)) < 0)
- debug("tap: failed to send %lu bytes (IPv4)", len);
- } else {
- struct ipv6hdr *ip6h = (struct ipv6hdr *)(eh + 1);
- char *data = (char *)(ip6h + 1);
-
- eh->h_proto = ntohs(ETH_P_IPV6);
-
- memset(ip6h->flow_lbl, 0, 3);
- ip6h->payload_len = htons(len);
- ip6h->priority = 0;
-
- ip6h->saddr = *src;
- ip6h->daddr = *tap_ip6_daddr(c, src);
-
- memcpy(data, in, len);
-
- ip6h->hop_limit = proto;
- ip6h->version = 0;
- ip6h->nexthdr = 0;
-
- if (proto == IPPROTO_UDP) {
- struct udphdr *uh = (struct udphdr *)(ip6h + 1);
-
- csum_udp6(uh, &ip6h->saddr, &ip6h->daddr,
- uh + 1, len - sizeof(*uh));
- } else if (proto == IPPROTO_ICMPV6) {
- struct icmp6hdr *ih = (struct icmp6hdr *)(ip6h + 1);
+/**
+ * tap_ip4_send() - Send IPv4 packet, with L2 headers, calculating L3/L4 checksums
+ * @c: Execution context
+ * @src: IPv4 source address
+ * @proto: L4 protocol number
+ * @in: Payload
+ * @len: L4 payload length
+ */
+void tap_ip4_send(const struct ctx *c, in_addr_t src, uint8_t proto,
+ const char *in, size_t len)
+{
+ char buf[USHRT_MAX];
+ struct iphdr *ip4h = (struct iphdr *)tap_push_l2h(c, buf, ETH_P_IP);
+ char *data = (char *)(ip4h + 1);
+
+ ip4h->version = 4;
+ ip4h->ihl = sizeof(struct iphdr) / 4;
+ ip4h->tos = 0;
+ ip4h->tot_len = htons(len + sizeof(*ip4h));
+ ip4h->id = 0;
+ ip4h->frag_off = 0;
+ ip4h->ttl = 255;
+ ip4h->protocol = proto;
+ ip4h->saddr = src;
+ ip4h->daddr = tap_ip4_daddr(c);
+ csum_ip4_header(ip4h);
+
+ memcpy(data, in, len);
+
+ if (ip4h->protocol == IPPROTO_UDP) {
+ struct udphdr *uh = (struct udphdr *)(ip4h + 1);
+
+ csum_udp4(uh, ip4h->saddr, ip4h->daddr,
+ uh + 1, len - sizeof(*uh));
+ } else if (ip4h->protocol == IPPROTO_ICMP) {
+ struct icmphdr *ih = (struct icmphdr *)(ip4h + 1);
+ csum_icmp4(ih, ih + 1, len - sizeof(*ih));
+ }
- csum_icmp6(ih, &ip6h->saddr, &ip6h->daddr,
- ih + 1, len - sizeof(*ih));
- }
- ip6h->version = 6;
- ip6h->nexthdr = proto;
- ip6h->hop_limit = 255;
- if (flow) {
- ip6h->flow_lbl[0] = (flow >> 16) & 0xf;
- ip6h->flow_lbl[1] = (flow >> 8) & 0xff;
- ip6h->flow_lbl[2] = (flow >> 0) & 0xff;
- }
+ if (tap_send(c, buf, len + (data - buf)) < 0)
+ debug("tap: failed to send %lu bytes (IPv4)", len);
+}
- if (tap_send(c, buf, len + sizeof(*ip6h) + sizeof(*eh)) < 1)
- debug("tap: failed to send %lu bytes (IPv6)", len);
+/**
+ * tap_ip6_send() - Send IPv6 packet, with L2 headers, calculating L3/L4 checksums
+ * @c: Execution context
+ * @src: IPv6 source address
+ * @proto: L4 protocol number
+ * @in: Payload
+ * @len: L4 payload length
+ * @flow: Flow label
+ */
+void tap_ip6_send(const struct ctx *c, const struct in6_addr *src,
+ uint8_t proto, const char *in, size_t len, uint32_t flow)
+{
+ char buf[USHRT_MAX];
+ struct ipv6hdr *ip6h =
+ (struct ipv6hdr *)tap_push_l2h(c, buf, ETH_P_IPV6);
+ char *data = (char *)(ip6h + 1);
+
+ ip6h->payload_len = htons(len);
+ ip6h->priority = 0;
+ ip6h->version = 6;
+ ip6h->nexthdr = proto;
+ ip6h->hop_limit = 255;
+ ip6h->saddr = *src;
+ ip6h->daddr = *tap_ip6_daddr(c, src);
+ ip6h->flow_lbl[0] = (flow >> 16) & 0xf;
+ ip6h->flow_lbl[1] = (flow >> 8) & 0xff;
+ ip6h->flow_lbl[2] = (flow >> 0) & 0xff;
+
+ memcpy(data, in, len);
+
+ if (proto == IPPROTO_UDP) {
+ struct udphdr *uh = (struct udphdr *)(ip6h + 1);
+
+ csum_udp6(uh, &ip6h->saddr, &ip6h->daddr,
+ uh + 1, len - sizeof(*uh));
+ } else if (proto == IPPROTO_ICMPV6) {
+ struct icmp6hdr *ih = (struct icmp6hdr *)(ip6h + 1);
+
+ csum_icmp6(ih, &ip6h->saddr, &ip6h->daddr,
+ ih + 1, len - sizeof(*ih));
}
+
+ if (tap_send(c, buf, len + (data - buf)) < 1)
+ debug("tap: failed to send %lu bytes (IPv6)", len);
}
PACKET_POOL_DECL(pool_l4, UIO_MAXIOV, pkt_buf);
diff --git a/tap.h b/tap.h
index a8da8bb..011ba8e 100644
--- a/tap.h
+++ b/tap.h
@@ -9,8 +9,10 @@
in_addr_t tap_ip4_daddr(const struct ctx *c);
const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
const struct in6_addr *src);
-void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
- const char *in, size_t len, uint32_t flow);
+void tap_ip4_send(const struct ctx *c, in_addr_t src, uint8_t proto,
+ const char *in, size_t len);
+void tap_ip6_send(const struct ctx *c, const struct in6_addr *src,
+ uint8_t proto, const char *in, size_t len, uint32_t flow);
int tap_send(const struct ctx *c, const void *data, size_t len);
void tap_handler(struct ctx *c, int fd, uint32_t events,
const struct timespec *now);
--
2.37.3