passt: Add IPv6 and NDP support, further fixes for IPv4 CT

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

ndp.c

@@ -0,0 +1,133 @@
+/* PASST - Plug A Simple Socket Transport
+ *
+ * ndp.c - NDP support for PASST
+ *
+ * Author: Stefano Brivio <sbrivio@redhat.com>
+ * License: GPLv2
+ *
+ */
+
+#include <stdio.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <string.h>
+#include <linux/if_ether.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <linux/icmpv6.h>
+#include <linux/udp.h>
+#include <net/if.h>
+#include <net/if_arp.h>
+#include <arpa/inet.h>
+
+#include "passt.h"
+#include "util.h"
+
+#define RS	133
+#define RA	134
+#define NS	135
+#define NA	136
+
+/**
+ * ndp() - Check for NDP solicitations, reply as needed
+ * @c:		Execution context
+ * @len:	Total L2 packet length
+ * @eh:		Packet buffer, Ethernet header
+ *
+ * Return: 0 if not handled here, 1 if handled, -1 on failure
+ */
+int ndp(struct ctx *c, unsigned len, struct ethhdr *eh)
+{
+	struct ethhdr *ehr;
+	struct ipv6hdr *ip6h = (struct ipv6hdr *)(eh + 1), *ip6hr;
+	struct icmp6hdr *ih, *ihr;
+	char buf[BUFSIZ] = { 0 };
+	uint8_t proto, *p;
+
+	ih = (struct icmp6hdr *)ipv6_l4hdr(ip6h, &proto);
+	if (!ih)
+		return -1;
+
+	if (proto != IPPROTO_ICMPV6 ||
+	    ih->icmp6_type < RS || ih->icmp6_type > NA)
+		return 0;
+
+	ehr = (struct ethhdr *)buf;
+	ip6hr = (struct ipv6hdr *)(ehr + 1);
+	ihr = (struct icmp6hdr *)(ip6hr + 1);
+
+	if (ih->icmp6_type == NS) {
+		fprintf(stderr, "NDP: received NS, sending NA\n");
+		ihr->icmp6_type = NA;
+		ihr->icmp6_code = 0;
+		ihr->icmp6_router = 1;
+		ihr->icmp6_solicited = 1;
+		ihr->icmp6_override = 1;
+
+		p = (unsigned char *)(ihr + 1);
+		memcpy(p, &c->gw6, sizeof(c->gw6));	/* target address */
+		p += 16;
+		*p++ = 2;			/* target ll */
+		*p++ = 1;			/* length */
+		memcpy(p, c->mac, ETH_ALEN);
+		p += 6;
+	} else if (ih->icmp6_type == RS) {
+		fprintf(stderr, "NDP: received RS, sending RA\n");
+		ihr->icmp6_type = RA;
+		ihr->icmp6_code = 0;
+		ihr->icmp6_rt_lifetime = htons(3600);
+
+		p = (unsigned char *)(ihr + 1);
+		p += 8;				/* reachable, retrans time */
+		*p++ = 3;			/* prefix */
+		*p++ = 4;			/* length */
+		*p++ = 64;			/* prefix length */
+		*p++ = 0xc0;			/* flags: L, A */
+		*(uint32_t *)p = htonl(3600);	/* lifetime */
+		p += 4;
+		*(uint32_t *)p = htonl(3600);	/* preferred lifetime */
+		p += 8;
+		memcpy(p, &c->addr6, 8);	/* prefix */
+		p += 16;
+
+		*p++ = 25;			/* RDNS */
+		*p++ = 3;			/* length */
+		p += 2;
+		*(uint32_t *)p = htonl(60);	/* lifetime */
+		p += 4;
+		memcpy(p, &c->dns6, 16);	/* address */
+		p += 16;
+
+		*p++ = 1;			/* source ll */
+		*p++ = 1;			/* length */
+		memcpy(p, c->mac, ETH_ALEN);
+		p += 6;
+	} else {
+		return 1;
+	}
+
+	len = (uintptr_t)p - (uintptr_t)ihr - sizeof(*ihr);
+
+	ip6hr->daddr = ip6h->saddr;
+	ip6hr->saddr = c->gw6;
+	ip6hr->payload_len = htons(sizeof(*ihr) + len);
+	ip6hr->hop_limit = IPPROTO_ICMPV6;
+	ihr->icmp6_cksum = 0;
+	ihr->icmp6_cksum = csum_ip4(ip6hr, sizeof(*ip6hr) +
+					   sizeof(*ihr) + len);
+
+	ip6hr->version = 6;
+	ip6hr->nexthdr = IPPROTO_ICMPV6;
+	ip6hr->hop_limit = 255;
+
+	len += sizeof(*ehr) + sizeof(*ip6hr) + sizeof(*ihr);
+	memcpy(ehr->h_dest, eh->h_source, ETH_ALEN);
+	memcpy(ehr->h_source, c->mac, ETH_ALEN);
+	ehr->h_proto = htons(ETH_P_IPV6);
+
+	if (send(c->fd_unix, ehr, len, 0) < 0)
+		perror("NDP: send");
+
+	return 1;
+}