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Split tap_ip_send() into IPv4 and IPv6 specific functions

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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@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2022-10-19 11:43:52 +11:00 committed by Stefano Brivio
parent fb5d1c5d7d
commit f616ca231e
4 changed files with 101 additions and 94 deletions
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4
dhcpv6.c
View file

@ -531,7 +531,7 @@ int dhcpv6(struct ctx *c, const struct pool *p,
resp_not_on_link.hdr.xid = mh->xid;
tap_ip_send(c, src, IPPROTO_UDP,
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;

10
icmp.c
View file

@ -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);
}
}

121
tap.c
View file

@ -113,77 +113,97 @@ 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);
/**
* 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);
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);
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 (iph->protocol == IPPROTO_UDP) {
struct udphdr *uh = (struct udphdr *)(iph + 1);
if (ip4h->protocol == IPPROTO_UDP) {
struct udphdr *uh = (struct udphdr *)(ip4h + 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_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));
}
if (tap_send(c, buf, len + sizeof(*iph) + sizeof(*eh)) < 0)
if (tap_send(c, buf, len + (data - buf)) < 0)
debug("tap: failed to send %lu bytes (IPv4)", len);
} else {
struct ipv6hdr *ip6h = (struct ipv6hdr *)(eh + 1);
}
/**
* 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);
eh->h_proto = ntohs(ETH_P_IPV6);
memset(ip6h->flow_lbl, 0, 3);
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);
ip6h->hop_limit = proto;
ip6h->version = 0;
ip6h->nexthdr = 0;
if (proto == IPPROTO_UDP) {
struct udphdr *uh = (struct udphdr *)(ip6h + 1);
@ -195,18 +215,9 @@ void tap_ip_send(const struct ctx *c, const struct in6_addr *src, uint8_t proto,
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 + sizeof(*ip6h) + sizeof(*eh)) < 1)
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);

6
tap.h
View file

@ -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);