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-rw-r--r--vrrpd/vrrp_packet.c326
1 files changed, 326 insertions, 0 deletions
diff --git a/vrrpd/vrrp_packet.c b/vrrpd/vrrp_packet.c
new file mode 100644
index 0000000..991c030
--- /dev/null
+++ b/vrrpd/vrrp_packet.c
@@ -0,0 +1,326 @@
+/*
+ * VRRP packet crafting.
+ * Copyright (C) 2018-2019 Cumulus Networks, Inc.
+ * Quentin Young
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; see the file COPYING; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+#include <zebra.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+
+#include "lib/checksum.h"
+#include "lib/ipaddr.h"
+#include "lib/memory.h"
+
+#include "vrrp.h"
+#include "vrrp_debug.h"
+#include "vrrp_packet.h"
+
+DEFINE_MTYPE_STATIC(VRRPD, VRRP_PKT, "VRRP packet");
+
+/* clang-format off */
+static const char *const vrrp_packet_names[16] = {
+ [0] = "Unknown",
+ [VRRP_TYPE_ADVERTISEMENT] = "ADVERTISEMENT",
+ [2] = "Unknown",
+ [3] = "Unknown",
+ [4] = "Unknown",
+ [5] = "Unknown",
+ [6] = "Unknown",
+ [7] = "Unknown",
+ [8] = "Unknown",
+ [9] = "Unknown",
+ [10] = "Unknown",
+ [11] = "Unknown",
+ [12] = "Unknown",
+ [13] = "Unknown",
+ [14] = "Unknown",
+ [15] = "Unknown",
+};
+/* clang-format on */
+
+/*
+ * Compute the VRRP checksum.
+ *
+ * Checksum is not set in the packet, just computed.
+ *
+ * pkt
+ * VRRP packet, fully filled out except for checksum field.
+ *
+ * pktsize
+ * sizeof(*pkt)
+ *
+ * src
+ * IP address that pkt will be transmitted from.
+ *
+ * Returns:
+ * VRRP checksum in network byte order.
+ */
+static uint16_t vrrp_pkt_checksum(struct vrrp_pkt *pkt, size_t pktsize,
+ struct ipaddr *src)
+{
+ uint16_t chksum;
+ bool v6 = (src->ipa_type == IPADDR_V6);
+
+ uint16_t chksum_pre = pkt->hdr.chksum;
+
+ pkt->hdr.chksum = 0;
+
+ if (v6) {
+ struct ipv6_ph ph = {};
+
+ ph.src = src->ipaddr_v6;
+ inet_pton(AF_INET6, VRRP_MCASTV6_GROUP_STR, &ph.dst);
+ ph.ulpl = htons(pktsize);
+ ph.next_hdr = IPPROTO_VRRP;
+ chksum = in_cksum_with_ph6(&ph, pkt, pktsize);
+ } else if (!v6 && ((pkt->hdr.vertype >> 4) == 3)) {
+ struct ipv4_ph ph = {};
+
+ ph.src = src->ipaddr_v4;
+ inet_pton(AF_INET, VRRP_MCASTV4_GROUP_STR, &ph.dst);
+ ph.proto = IPPROTO_VRRP;
+ ph.len = htons(pktsize);
+ chksum = in_cksum_with_ph4(&ph, pkt, pktsize);
+ } else if (!v6 && ((pkt->hdr.vertype >> 4) == 2)) {
+ chksum = in_cksum(pkt, pktsize);
+ } else {
+ assert(!"Invalid VRRP protocol version");
+ }
+
+ pkt->hdr.chksum = chksum_pre;
+
+ return chksum;
+}
+
+ssize_t vrrp_pkt_adver_build(struct vrrp_pkt **pkt, struct ipaddr *src,
+ uint8_t version, uint8_t vrid, uint8_t prio,
+ uint16_t max_adver_int, uint8_t numip,
+ struct ipaddr **ips)
+{
+ bool v6 = false;
+ size_t addrsz = 0;
+
+ assert(version >= 2 && version <= 3);
+
+ if (numip > 0) {
+ v6 = IS_IPADDR_V6(ips[0]);
+ addrsz = IPADDRSZ(ips[0]);
+ }
+
+ assert(!(version == 2 && v6));
+
+ size_t pktsize = VRRP_PKT_SIZE(v6 ? AF_INET6 : AF_INET, version, numip);
+
+ *pkt = XCALLOC(MTYPE_VRRP_PKT, pktsize);
+
+ (*pkt)->hdr.vertype |= version << 4;
+ (*pkt)->hdr.vertype |= VRRP_TYPE_ADVERTISEMENT;
+ (*pkt)->hdr.vrid = vrid;
+ (*pkt)->hdr.priority = prio;
+ (*pkt)->hdr.naddr = numip;
+ if (version == 3)
+ (*pkt)->hdr.v3.adver_int = htons(max_adver_int);
+ else if (version == 2) {
+ (*pkt)->hdr.v2.auth_type = 0;
+ (*pkt)->hdr.v2.adver_int = MAX(max_adver_int / 100, 1);
+ }
+
+ uint8_t *aptr = (void *)(*pkt)->addrs;
+
+ for (int i = 0; i < numip; i++) {
+ memcpy(aptr, &ips[i]->ip.addr, addrsz);
+ aptr += addrsz;
+ }
+
+ (*pkt)->hdr.chksum = vrrp_pkt_checksum(*pkt, pktsize, src);
+
+ return pktsize;
+}
+
+void vrrp_pkt_free(struct vrrp_pkt *pkt)
+{
+ XFREE(MTYPE_VRRP_PKT, pkt);
+}
+
+size_t vrrp_pkt_adver_dump(char *buf, size_t buflen, struct vrrp_pkt *pkt)
+{
+ if (buflen < 1)
+ return 0;
+
+ char tmpbuf[BUFSIZ];
+ size_t rs = 0;
+ struct vrrp_hdr *hdr = &pkt->hdr;
+
+ buf[0] = 0x00;
+ snprintf(tmpbuf, sizeof(tmpbuf), "version %u, ", (hdr->vertype >> 4));
+ rs += strlcat(buf, tmpbuf, buflen);
+ snprintf(tmpbuf, sizeof(tmpbuf), "type %u (%s), ",
+ (hdr->vertype & 0x0F),
+ vrrp_packet_names[(hdr->vertype & 0x0F)]);
+ rs += strlcat(buf, tmpbuf, buflen);
+ snprintf(tmpbuf, sizeof(tmpbuf), "vrid %u, ", hdr->vrid);
+ rs += strlcat(buf, tmpbuf, buflen);
+ snprintf(tmpbuf, sizeof(tmpbuf), "priority %u, ", hdr->priority);
+ rs += strlcat(buf, tmpbuf, buflen);
+ snprintf(tmpbuf, sizeof(tmpbuf), "#%u addresses, ", hdr->naddr);
+ rs += strlcat(buf, tmpbuf, buflen);
+ snprintf(tmpbuf, sizeof(tmpbuf), "max adver int %u, ",
+ ntohs(hdr->v3.adver_int));
+ rs += strlcat(buf, tmpbuf, buflen);
+ snprintf(tmpbuf, sizeof(tmpbuf), "checksum %x", ntohs(hdr->chksum));
+ rs += strlcat(buf, tmpbuf, buflen);
+
+ return rs;
+}
+
+ssize_t vrrp_pkt_parse_datagram(int family, int version, struct msghdr *m,
+ size_t read, struct ipaddr *src,
+ struct vrrp_pkt **pkt, char *errmsg,
+ size_t errmsg_len)
+{
+ /* Source (MAC & IP), Dest (MAC & IP) TTL validation done by kernel */
+ size_t addrsz = (family == AF_INET) ? sizeof(struct in_addr)
+ : sizeof(struct in6_addr);
+
+ size_t pktsize;
+ uint8_t *buf = m->msg_iov->iov_base;
+
+#define VRRP_PKT_VCHECK(cond, _f, ...) \
+ do { \
+ if (!(cond)) { \
+ if (errmsg) \
+ snprintf(errmsg, errmsg_len, (_f), \
+ ##__VA_ARGS__); \
+ return -1; \
+ } \
+ } while (0)
+
+ /* IPvX header check */
+
+ if (family == AF_INET) {
+ VRRP_PKT_VCHECK(
+ read >= sizeof(struct ip),
+ "Datagram not large enough to contain IP header");
+
+ struct ip *ip = (struct ip *)buf;
+
+ /* IP total length check */
+ VRRP_PKT_VCHECK(
+ ntohs(ip->ip_len) == read,
+ "IPv4 packet length field does not match # received bytes; %hu!= %zu",
+ ntohs(ip->ip_len), read);
+
+ /* TTL check */
+ VRRP_PKT_VCHECK(ip->ip_ttl == 255,
+ "IPv4 TTL is %hhu; should be 255",
+ ip->ip_ttl);
+
+ *pkt = (struct vrrp_pkt *)(buf + (ip->ip_hl << 2));
+ pktsize = read - (ip->ip_hl << 2);
+
+ /* IP empty packet check */
+ VRRP_PKT_VCHECK(pktsize > 0, "IPv4 packet has no payload");
+
+ /* Extract source address */
+ struct sockaddr_in *sa = m->msg_name;
+
+ src->ipa_type = IPADDR_V4;
+ src->ipaddr_v4 = sa->sin_addr;
+ } else if (family == AF_INET6) {
+ struct cmsghdr *c;
+
+ for (c = CMSG_FIRSTHDR(m); c != NULL; CMSG_NXTHDR(m, c)) {
+ if (c->cmsg_level == IPPROTO_IPV6
+ && c->cmsg_type == IPV6_HOPLIMIT)
+ break;
+ }
+
+ VRRP_PKT_VCHECK(!!c, "IPv6 Hop Limit not received");
+
+ uint8_t *hoplimit = CMSG_DATA(c);
+
+ VRRP_PKT_VCHECK(*hoplimit == 255,
+ "IPv6 Hop Limit is %hhu; should be 255",
+ *hoplimit);
+
+ *pkt = (struct vrrp_pkt *)buf;
+ pktsize = read;
+
+ /* Extract source address */
+ struct sockaddr_in6 *sa = m->msg_name;
+
+ src->ipa_type = IPADDR_V6;
+ memcpy(&src->ipaddr_v6, &sa->sin6_addr,
+ sizeof(struct in6_addr));
+ } else {
+ assert(!"Unknown address family");
+ }
+
+ /* Size check */
+ size_t minsize = (family == AF_INET) ? VRRP_MIN_PKT_SIZE_V4
+ : VRRP_MIN_PKT_SIZE_V6;
+ size_t maxsize = (family == AF_INET) ? VRRP_MAX_PKT_SIZE_V4
+ : VRRP_MAX_PKT_SIZE_V6;
+ VRRP_PKT_VCHECK(pktsize >= minsize,
+ "VRRP packet is undersized (%zu < %zu)", pktsize,
+ minsize);
+ VRRP_PKT_VCHECK(pktsize <= maxsize,
+ "VRRP packet is oversized (%zu > %zu)", pktsize,
+ maxsize);
+
+ /* Version check */
+ uint8_t pktver = (*pkt)->hdr.vertype >> 4;
+
+ VRRP_PKT_VCHECK(pktver == version, "Bad version %u", pktver);
+
+ /* Checksum check */
+ uint16_t chksum = vrrp_pkt_checksum(*pkt, pktsize, src);
+
+ VRRP_PKT_VCHECK((*pkt)->hdr.chksum == chksum,
+ "Bad VRRP checksum %hx; should be %hx",
+ (*pkt)->hdr.chksum, chksum);
+
+ /* Type check */
+ VRRP_PKT_VCHECK(((*pkt)->hdr.vertype & 0x0F) == 1, "Bad type %u",
+ (*pkt)->hdr.vertype & 0x0f);
+
+ /* Exact size check */
+ size_t ves = VRRP_PKT_SIZE(family, pktver, (*pkt)->hdr.naddr);
+
+ VRRP_PKT_VCHECK(pktsize == ves, "Packet has incorrect # addresses%s",
+ pktver == 2 ? " or missing auth fields" : "");
+
+ /* auth type check */
+ if (version == 2)
+ VRRP_PKT_VCHECK((*pkt)->hdr.v2.auth_type == 0,
+ "Bad authentication type %hhu",
+ (*pkt)->hdr.v2.auth_type);
+
+ /* Addresses check */
+ char vbuf[INET6_ADDRSTRLEN];
+ uint8_t *p = (uint8_t *)(*pkt)->addrs;
+
+ for (uint8_t i = 0; i < (*pkt)->hdr.naddr; i++) {
+ VRRP_PKT_VCHECK(inet_ntop(family, p, vbuf, sizeof(vbuf)),
+ "Bad IP address, #%hhu", i);
+ p += addrsz;
+ }
+
+ /* Everything checks out */
+ return pktsize;
+}
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