diff options
Diffstat (limited to 'passt.c')
| -rw-r--r-- | passt.c | 666 |
1 files changed, 666 insertions, 0 deletions
@@ -0,0 +1,666 @@ +/* PASST - Plug A Simple Socket Transport + * + * passt.c - Daemon implementation + * + * Author: Stefano Brivio <sbrivio@redhat.com> + * License: GPLv2 + * + * Grab Ethernet frames via AF_UNIX socket, build AF_INET sockets for each + * 5-tuple from ICMP, TCP, UDP packets, perform connection tracking and forward + * them with destination address NAT. Forward packets received on sockets back + * to the UNIX domain socket (typically, a tap file descriptor from qemu). + * + * TODO: + * - steal packets from AF_INET sockets (using eBPF/XDP, or a new socket + * option): currently, incoming packets are also handled by in-kernel protocol + * handlers, so every incoming untracked TCP packet gets a RST. Workaround: + * iptables -A OUTPUT -m state --state INVALID,NEW,ESTABLISHED \ + * -p tcp --tcp-flags RST RST -j DROP + * - and use XDP sockmap on top of that to improve performance + * - add IPv6 support. Current workaround on the namespace or machine on the + * tap side: + * echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6 + * - reserve and translate ports + * - aging and timeout/RST bookkeeping for connection tracking entries + */ + +#include <stdio.h> +#include <sys/epoll.h> +#include <sys/socket.h> +#include <sys/types.h> +#include <sys/ioctl.h> +#include <sys/un.h> +#include <ifaddrs.h> +#include <linux/if_ether.h> +#include <linux/if_packet.h> +#include <linux/ip.h> +#include <linux/ipv6.h> +#include <linux/tcp.h> +#include <linux/udp.h> +#include <linux/if_link.h> +#include <net/ethernet.h> +#include <stdlib.h> +#include <unistd.h> +#include <arpa/inet.h> +#include <net/if.h> +#include <netdb.h> +#include <string.h> +#include <errno.h> +#include <linux/ip.h> +#include <linux/netlink.h> +#include <linux/rtnetlink.h> + +#include "passt.h" +#include "arp.h" +#include "dhcp.h" +#include "util.h" + +#define EPOLL_EVENTS 10 + +/** + * sock_unix() - Create and bind AF_UNIX socket, add to epoll list + * + * Return: newly created socket, doesn't return on error + */ +static int sock_unix(void) +{ + int fd = socket(AF_UNIX, SOCK_STREAM, 0); + struct sockaddr_un addr = { + .sun_family = AF_UNIX, + .sun_path = UNIX_SOCK_PATH, + }; + + if (fd < 0) { + perror("UNIX socket"); + exit(EXIT_FAILURE); + } + + unlink(UNIX_SOCK_PATH); + if (bind(fd, (const struct sockaddr *)&addr, sizeof(addr)) < 0) { + perror("UNIX socket bind"); + exit(EXIT_FAILURE); + } + return fd; +} + +/** + * struct nl_request - Netlink request filled and sent by get_routes() + * @nlh: Netlink message header + * @rtm: Routing Netlink message + */ +struct nl_request { + struct nlmsghdr nlh; + struct rtmsg rtm; +}; + +/** + * get_routes() - Get default route and fill in routable interface name + * @c: Execution context + */ +static void get_routes(struct ctx *c) +{ + struct nl_request req = { + .nlh.nlmsg_type = RTM_GETROUTE, + .nlh.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP | NLM_F_EXCL, + .nlh.nlmsg_len = sizeof(struct nl_request), + .nlh.nlmsg_seq = 1, + .rtm.rtm_family = AF_INET, + .rtm.rtm_table = RT_TABLE_MAIN, + .rtm.rtm_scope = RT_SCOPE_UNIVERSE, + .rtm.rtm_type = RTN_UNICAST, + }; + struct sockaddr_nl addr = { + .nl_family = AF_NETLINK, + }; + int s, n, na, found = 0; + struct nlmsghdr *nlh; + struct rtattr *rta; + struct rtmsg *rtm; + char buf[BUFSIZ]; + + s = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE); + if (s < 0) { + perror("netlink socket"); + goto out; + } + + if (bind(s, (struct sockaddr *)&addr, sizeof(addr)) < 0) { + perror("netlink bind"); + goto out; + } + + if (send(s, &req, sizeof(req), 0) < 0) { + perror("netlink send"); + goto out; + } + + n = recv(s, &buf, sizeof(buf), 0); + if (n < 0) { + perror("netlink recv"); + goto out; + } + + nlh = (struct nlmsghdr *)buf; + if (nlh->nlmsg_type == NLMSG_DONE) + goto out; + + for ( ; NLMSG_OK(nlh, n) && found < 2; NLMSG_NEXT(nlh, n)) { + rtm = (struct rtmsg *)NLMSG_DATA(nlh); + + if (rtm->rtm_dst_len) + continue; + + rta = (struct rtattr *)RTM_RTA(rtm); + na = RTM_PAYLOAD(nlh); + for ( ; RTA_OK(rta, na) && found < 2; rta = RTA_NEXT(rta, na)) { + if (rta->rta_type == RTA_GATEWAY) { + memcpy(&c->gw4, RTA_DATA(rta), sizeof(c->gw4)); + found++; + } + + if (rta->rta_type == RTA_OIF) { + if_indextoname(*(unsigned *)RTA_DATA(rta), + c->ifn); + found++; + } + } + } + +out: + close(s); + + if (found < 2) { + fprintf(stderr, "No routing information\n"); + exit(EXIT_FAILURE); + } +} + +/** + * get_addrs() - Fetch MAC, IP addresses, masks of external routable interface + * @c: Execution context + */ +static void get_addrs(struct ctx *c) +{ + struct ifreq ifr = { + .ifr_addr.sa_family = AF_INET, + }; + struct ifaddrs *ifaddr, *ifa; + int s; + + if (getifaddrs(&ifaddr) == -1) { + perror("getifaddrs"); + goto out; + } + + for (ifa = ifaddr; ifa && !c->addr4; ifa = ifa->ifa_next) { + struct sockaddr_in *in_addr; + + if (strcmp(ifa->ifa_name, c->ifn)) + continue; + + if (!ifa->ifa_addr) + continue; + + if (ifa->ifa_addr->sa_family != AF_INET) + continue; + + in_addr = (struct sockaddr_in *)ifa->ifa_addr; + c->addr4 = in_addr->sin_addr.s_addr; + in_addr = (struct sockaddr_in *)ifa->ifa_netmask; + c->mask4 = in_addr->sin_addr.s_addr; + } + + freeifaddrs(ifaddr); + + s = socket(AF_INET, SOCK_DGRAM, 0); + if (s < 0) { + perror("socket SIOCGIFHWADDR"); + goto out; + } + + strncpy(ifr.ifr_name, c->ifn, IF_NAMESIZE); + if (ioctl(s, SIOCGIFHWADDR, &ifr) < 0) { + perror("SIOCGIFHWADDR"); + goto out; + } + + close(s); + memcpy(c->mac, ifr.ifr_hwaddr.sa_data, ETH_ALEN); + + return; +out: + fprintf(stderr, "Couldn't get addresses for routable interface\n"); + exit(EXIT_FAILURE); +} + +/** + * get_dns() - Get nameserver addresses from local /etc/resolv.conf + * @c: Execution context + */ +static void get_dns(struct ctx *c) +{ + char buf[BUFSIZ], *p, *nl; + int dns4 = 0; + FILE *r; + + r = fopen("/etc/resolv.conf", "r"); + while (fgets(buf, BUFSIZ, r) && !dns4) { + if (!strstr(buf, "nameserver ")) + continue; + p = strrchr(buf, ' '); + nl = strchr(buf, '\n'); + if (nl) + *nl = 0; + if (p && inet_pton(AF_INET, p + 1, &c->dns4)) + dns4 = 1; + } + + fclose(r); + if (dns4) + return; + + fprintf(stderr, "Couldn't get IPv4 nameserver address\n"); + exit(EXIT_FAILURE); +} + +/** + * sock4_l4() - Create and bind AF_INET socket for given L4, add to epoll list + * @c: Execution context + * @proto: Protocol number, network order + * @port: L4 port, network order + * + * Return: newly created socket, -1 on error + */ +static int sock4_l4(struct ctx *c, uint16_t proto, uint16_t port) +{ + struct sockaddr_in addr = { + .sin_family = AF_INET, + .sin_port = port, + .sin_addr = { .s_addr = c->addr4 }, + }; + struct epoll_event ev = { 0 }; + int fd; + + fd = socket(AF_INET, SOCK_RAW, proto); + if (fd < 0) { + perror("L4 socket"); + return -1; + } + + if (bind(fd, (const struct sockaddr *)&addr, sizeof(addr)) < 0) { + perror("L4 bind"); + close(fd); + return -1; + } + + ev.events = EPOLLIN; + ev.data.fd = fd; + if (epoll_ctl(c->epollfd, EPOLL_CTL_ADD, fd, &ev) == -1) { + perror("L4 epoll_ctl"); + return -1; + } + + return fd; +} + +/** + * lookup4() - Look up socket entry from tap-sourced packet, create if missing + * @c: Execution context + * @eh: Packet buffer, Ethernet header + * + * Return: -1 for unsupported or too many sockets, matching socket otherwise + */ +static int lookup4(struct ctx *c, const struct ethhdr *eh) +{ + struct iphdr *iph = (struct iphdr *)(eh + 1); + struct tcphdr *th = (struct tcphdr *)((char *)iph + iph->ihl * 4); + char buf_s[BUFSIZ], buf_d[BUFSIZ]; + struct ct4 *ct = c->map4; + int i, one_icmp_fd = 0; + + if (iph->protocol != IPPROTO_ICMP && iph->protocol != IPPROTO_TCP && + iph->protocol != IPPROTO_UDP) + return -1; + + for (i = 0; i < CT_SIZE; i++) { + if (ct[i].p == iph->protocol && ct[i].sa == iph->saddr && + ((ct[i].p == IPPROTO_ICMP && ct[i].da == iph->daddr) + || ct[i].sp == th->source) && + !memcmp(ct[i].hd, eh->h_dest, ETH_ALEN) && + !memcmp(ct[i].hs, eh->h_source, ETH_ALEN)) { + if (iph->protocol != IPPROTO_ICMP) { + ct[i].da = iph->daddr; + ct[i].dp = th->dest; + } + return ct[i].fd; + } + } + + for (i = 0; i < CT_SIZE && ct[i].p; i++) { + if (iph->protocol == IPPROTO_ICMP) + one_icmp_fd = ct[i].fd; + } + + if (i == CT_SIZE) { + fprintf(stderr, "\nToo many sockets, aborting "); + } else { + if (iph->protocol == IPPROTO_ICMP && one_icmp_fd) + ct[i].fd = one_icmp_fd; + else + ct[i].fd = sock4_l4(c, iph->protocol, th->source); + + fprintf(stderr, "\n(socket %i) New ", ct[i].fd); + ct[i].p = iph->protocol; + ct[i].sa = iph->saddr; + ct[i].da = iph->daddr; + if (iph->protocol != IPPROTO_ICMP) { + ct[i].sp = th->source; + ct[i].dp = th->dest; + } + memcpy(&ct[i].hd, eh->h_dest, ETH_ALEN); + memcpy(&ct[i].hs, eh->h_source, ETH_ALEN); + } + + if (iph->protocol == IPPROTO_ICMP) { + fprintf(stderr, "icmp connection\n\tfrom %s to %s\n\n", + inet_ntop(AF_INET, &iph->saddr, buf_s, sizeof(buf_s)), + inet_ntop(AF_INET, &iph->daddr, buf_d, sizeof(buf_d))); + } else { + fprintf(stderr, "%s connection\n\tfrom %s:%i to %s:%i\n\n", + getprotobynumber(iph->protocol)->p_name, + inet_ntop(AF_INET, &iph->saddr, buf_s, sizeof(buf_s)), + ntohs(th->source), + inet_ntop(AF_INET, &iph->daddr, buf_d, sizeof(buf_d)), + ntohs(th->dest)); + } + + return (i == CT_SIZE) ? -1 : ct[i].fd; +} + +/** + * lookup4_r4() - Reverse look up connection tracking entry from incoming packet + * @ct: Connection tracking table + * @fd: File descriptor that received the packet + * @iph: Packet buffer, IP header + * + * Return: matching entry if any, NULL otherwise + */ +struct ct4 *lookup_r4(struct ct4 *ct, int fd, struct iphdr *iph) +{ + struct tcphdr *th = (struct tcphdr *)((char *)iph + iph->ihl * 4); + int i; + + for (i = 0; i < CT_SIZE; i++) { + if (ct[i].fd == fd && + iph->protocol == ct[i].p && + iph->saddr == ct[i].da && + (iph->protocol == IPPROTO_ICMP || + (th->source == ct[i].dp && th->dest == ct[i].sp))) + return &ct[i]; + } + + return NULL; +} + +/** + * nat4_out() - Perform outgoing IPv4 address translation + * @addr: Source address to be used + * @iph: IP header + */ +static void nat4_out(unsigned long addr, struct iphdr *iph) +{ + iph->saddr = addr; +} + +/** + * nat4_in() - Perform incoming IPv4 address translation + * @addr: Original destination address to be used + * @iph: IP header + */ +static void nat_in(unsigned long addr, struct iphdr *iph) +{ + iph->daddr = addr; +} + +/** + * csum_ipv4() - Calculate TCP checksum for IPv4 and set in place + * @iph: Packet buffer, IP header + */ +static void csum_tcp4(struct iphdr *iph) +{ + struct tcphdr *th = (struct tcphdr *)((char *)iph + iph->ihl * 4); + uint16_t tlen = ntohs(iph->tot_len) - iph->ihl * 4, *p = (uint16_t *)th; + uint32_t sum = 0; + + sum += (iph->saddr >> 16) & 0xffff; + sum += iph->saddr & 0xffff; + sum += (iph->daddr >> 16) & 0xffff; + sum += iph->daddr & 0xffff; + + sum += htons(IPPROTO_TCP); + sum += htons(tlen); + + th->check = 0; + while (tlen > 1) { + sum += *p++; + tlen -= 2; + } + + if (tlen > 0) { + sum += *p & htons(0xff00); + } + + th->check = (uint16_t)~csum_fold(sum); +} + +/** + * tap4_handler() - Packet handler for tap file descriptor + * @c: Execution context + * @len: Total L2 packet length + * @in: Packet buffer, L2 headers + */ +static void tap4_handler(struct ctx *c, int len, char *in) +{ + struct ethhdr *eh = (struct ethhdr *)in; + struct iphdr *iph = (struct iphdr *)(eh + 1); + struct tcphdr *th = (struct tcphdr *)((char *)iph + iph->ihl * 4); + struct udphdr *uh = (struct udphdr *)th; + struct sockaddr_in addr = { + .sin_family = AF_INET, + .sin_port = th->dest, + .sin_addr = { .s_addr = iph->daddr }, + }; + char buf_s[BUFSIZ], buf_d[BUFSIZ]; + int fd; + + if (arp(c, len, eh) || dhcp(c, len, eh)) + return; + + fd = lookup4(c, eh); + if (fd == -1) + return; + + if (iph->protocol == IPPROTO_ICMP) { + fprintf(stderr, "icmp from tap: %s -> %s (socket %i)\n", + inet_ntop(AF_INET, &iph->saddr, buf_s, sizeof(buf_s)), + inet_ntop(AF_INET, &iph->daddr, buf_d, sizeof(buf_d)), + fd); + } else { + fprintf(stderr, "%s from tap: %s:%i -> %s:%i (socket %i)\n", + getprotobynumber(iph->protocol)->p_name, + inet_ntop(AF_INET, &iph->saddr, buf_s, sizeof(buf_s)), + ntohs(th->source), + inet_ntop(AF_INET, &iph->daddr, buf_d, sizeof(buf_d)), + ntohs(th->dest), + fd); + } + + if (iph->protocol == IPPROTO_TCP) + csum_tcp4(iph); + else if (iph->protocol == IPPROTO_UDP) + uh->check = 0; + else if (iph->protocol != IPPROTO_ICMP) + return; + + nat4_out(c->addr4, iph); + + if (sendto(fd, (void *)th, len - sizeof(*eh) - iph->ihl * 4, 0, + (struct sockaddr *)&addr, sizeof(addr)) < 0) + perror("sendto"); + +} + +/** + * ext4_handler() - Packet handler for external routable interface + * @c: Execution context + * @fd: File descriptor that received the packet + * @len: Total L3 packet length + * @in: Packet buffer, L3 headers + */ +static void ext4_handler(struct ctx *c, int fd, int len, char *in) +{ + struct iphdr *iph = (struct iphdr *)in; + struct tcphdr *th = (struct tcphdr *)((char *)iph + iph->ihl * 4); + struct udphdr *uh = (struct udphdr *)th; + char buf_s[BUFSIZ], buf_d[BUFSIZ], buf[ETH_MAX_MTU]; + struct ethhdr *eh = (struct ethhdr *)buf; + struct ct4 *entry; + + entry = lookup_r4(c->map4, fd, iph); + if (!entry) + return; + + nat_in(entry->sa, iph); + + iph->check = 0; + iph->check = csum_ip4(iph, iph->ihl * 4); + + if (iph->protocol == IPPROTO_TCP) + csum_tcp4(iph); + else if (iph->protocol == IPPROTO_UDP) + uh->check = 0; + + memcpy(eh->h_dest, entry->hs, ETH_ALEN); + memcpy(eh->h_source, entry->hd, ETH_ALEN); + eh->h_proto = ntohs(ETH_P_IP); + + memcpy(eh + 1, in, len); + + if (iph->protocol == IPPROTO_ICMP) { + fprintf(stderr, "icmp (socket %i) to tap: %s -> %s\n", + entry->fd, + inet_ntop(AF_INET, &iph->saddr, buf_s, sizeof(buf_s)), + inet_ntop(AF_INET, &iph->daddr, buf_d, sizeof(buf_d))); + } else { + fprintf(stderr, "%s (socket %i) to tap: %s:%i -> %s:%i\n", + getprotobynumber(iph->protocol)->p_name, + entry->fd, + inet_ntop(AF_INET, &iph->saddr, buf_s, sizeof(buf_s)), + ntohs(th->source), + inet_ntop(AF_INET, &iph->daddr, buf_d, sizeof(buf_d)), + ntohs(th->dest)); + } + + if (send(c->fd_unix, buf, len + sizeof(*eh), 0) < 0) + perror("send"); +} + +/** + * usage() - Print usage and exit + * @name: Executable name + */ +void usage(const char *name) +{ + fprintf(stderr, "Usage: %s\n", name); + + exit(EXIT_FAILURE); +} + +/** + * main() - Entry point and main loop + * @argc: Argument count + * @argv: Interface names + * + * Return: 0 once interrupted, non-zero on failure + */ +int main(int argc, char **argv) +{ + struct epoll_event events[EPOLL_EVENTS]; + char buf4[4][sizeof("255.255.255.255")]; + struct epoll_event ev = { 0 }; + char buf[ETH_MAX_MTU]; + struct ctx c = { 0 }; + int nfds, i, len; + int fd_unix; + + if (argc != 1) + usage(argv[0]); + + get_routes(&c); + get_addrs(&c); + get_dns(&c); + + fprintf(stderr, "ARP:\n"); + fprintf(stderr, "\taddress: %02x:%02x:%02x:%02x:%02x:%02x from %s\n", + c.mac[0], c.mac[1], c.mac[2], c.mac[3], c.mac[4], c.mac[5], + c.ifn); + fprintf(stderr, "DHCP:\n"); + fprintf(stderr, "\tassign: %s, mask: %s, router: %s, DNS: %s\n\n", + inet_ntop(AF_INET, &c.addr4, buf4[0], sizeof(buf4[0])), + inet_ntop(AF_INET, &c.mask4, buf4[1], sizeof(buf4[1])), + inet_ntop(AF_INET, &c.gw4, buf4[2], sizeof(buf4[2])), + inet_ntop(AF_INET, &c.dns4, buf4[3], sizeof(buf4[3]))); + + c.epollfd = epoll_create1(0); + if (c.epollfd == -1) { + perror("epoll_create1"); + exit(EXIT_FAILURE); + } + + fd_unix = sock_unix(); +listen: + listen(fd_unix, 1); + c.fd_unix = accept(fd_unix, NULL, NULL); + ev.events = EPOLLIN; + ev.data.fd = c.fd_unix; + epoll_ctl(c.epollfd, EPOLL_CTL_ADD, c.fd_unix, &ev); + fprintf(stderr, + "You can now start qrap:\n\t" + "./qrap 42 kvm ... -net tap,fd=42 -net nic,model=virtio\n\n"); + +loop: + nfds = epoll_wait(c.epollfd, events, EPOLL_EVENTS, -1); + if (nfds == -1 && errno != EINTR) { + perror("epoll_wait"); + exit(EXIT_FAILURE); + } + + for (i = 0; i < nfds; i++) { + len = recv(events[i].data.fd, buf, sizeof(buf), MSG_DONTWAIT); + + if (events[i].data.fd == c.fd_unix && len <= 0) { + epoll_ctl(c.epollfd, EPOLL_CTL_DEL, c.fd_unix, &ev); + close(c.fd_unix); + goto listen; + } + + if (len == 0 || (len < 0 && errno == EINTR)) + continue; + + if (len < 0) { + if (errno == EAGAIN || errno == EWOULDBLOCK) + break; + goto out; + } + + if (events[i].data.fd == c.fd_unix) + tap4_handler(&c, len, buf); + else + ext4_handler(&c, events[i].data.fd, len, buf); + } + + goto loop; + +out: + return 0; +} |