Merge pull request #1288 from teg/ipv4acd-3

sd-ipv4acd: split out as separate library from sd-ipv4ll

1 files changed, 153 insertions, 0 deletions

diff --git a/src/libsystemd-network/arp-util.c b/src/libsystemd-network/arp-util.c
new file mode 100644
index 0000000000..2f5b9b3731
--- /dev/null
+++ b/src/libsystemd-network/arp-util.c
@@ -0,0 +1,153 @@
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2014 Axis Communications AB. All rights reserved.
+  Copyright (C) 2015 Tom Gundersen
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <linux/filter.h>
+#include <arpa/inet.h>
+
+#include "util.h"
+#include "arp-util.h"
+
+int arp_network_bind_raw_socket(int ifindex, be32_t address, const struct ether_addr *eth_mac) {
+        struct sock_filter filter[] = {
+                BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                         /* A <- packet length */
+                BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(struct ether_arp), 1, 0),           /* packet >= arp packet ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hrd)), /* A <- header */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0),                       /* header == ethernet ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pro)), /* A <- protocol */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 1, 0),                       /* protocol == IP ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hln)), /* A <- hardware address length */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct ether_addr), 1, 0),          /* length == sizeof(ether_addr)? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pln)), /* A <- protocol address length */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct in_addr), 1, 0),             /* length == sizeof(in_addr) ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_op)),  /* A <- operation */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REQUEST, 2, 0),                      /* protocol == request ? */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REPLY, 1, 0),                        /* protocol == reply ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                /* Sender Hardware Address must be different from our own */
+                BPF_STMT(BPF_LD + BPF_IMM, htobe32(*((uint32_t *) eth_mac))),                  /* A <- 4 bytes of client's MAC */
+                BPF_STMT(BPF_MISC + BPF_TAX, 0),                                               /* X <- A */
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_sha)),       /* A <- 4 bytes of SHA */
+                BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                        /* A xor X */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 6),                                  /* A == 0 ? */
+                BPF_STMT(BPF_LD + BPF_IMM, htobe16(*((uint16_t *) (((char *) eth_mac) + 4)))), /* A <- remainder of client's MAC */
+                BPF_STMT(BPF_MISC + BPF_TAX, 0),                                               /* X <- A */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, arp_sha) + 4),   /* A <- remainder of SHA */
+                BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                        /* A xor X */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1),                                  /* A == 0 ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                /* Sender Protocol Address or Target Protocol Address must be equal to the one we care about*/
+                BPF_STMT(BPF_LD + BPF_IMM, htobe32(address)),                                  /* A <- clients IP */
+                BPF_STMT(BPF_MISC + BPF_TAX, 0),                                               /* X <- A */
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_spa)),       /* A <- SPA */
+                BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                        /* X xor A */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1),                                  /* A == 0 ? */
+                BPF_STMT(BPF_RET + BPF_K, 65535),                                              /* return all */
+                BPF_STMT(BPF_LD + BPF_IMM, htobe32(address)),                                  /* A <- clients IP */
+                BPF_STMT(BPF_MISC + BPF_TAX, 0),                                               /* X <- A */
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_tpa)),       /* A <- TPA */
+                BPF_STMT(BPF_ALU + BPF_XOR + BPF_X, 0),                                        /* X xor A */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 0, 1),                                  /* A == 0 ? */
+                BPF_STMT(BPF_RET + BPF_K, 65535),                                              /* return all */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+        };
+        struct sock_fprog fprog = {
+                .len = ELEMENTSOF(filter),
+                .filter = (struct sock_filter*) filter
+        };
+        union sockaddr_union link = {
+                .ll.sll_family = AF_PACKET,
+                .ll.sll_protocol = htons(ETH_P_ARP),
+                .ll.sll_ifindex = ifindex,
+                .ll.sll_halen = ETH_ALEN,
+                .ll.sll_addr = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
+        };
+        _cleanup_close_ int s = -1;
+        int r;
+
+        assert(ifindex > 0);
+
+        s = socket(PF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
+        if (s < 0)
+                return -errno;
+
+        r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
+        if (r < 0)
+                return -errno;
+
+        r = bind(s, &link.sa, sizeof(link.ll));
+        if (r < 0)
+                return -errno;
+
+        r = s;
+        s = -1;
+
+        return r;
+}
+
+static int arp_send_packet(int fd, int ifindex,
+                           be32_t pa, const struct ether_addr *ha,
+                           bool announce) {
+        union sockaddr_union link = {
+                .ll.sll_family = AF_PACKET,
+                .ll.sll_protocol = htons(ETH_P_ARP),
+                .ll.sll_ifindex = ifindex,
+                .ll.sll_halen = ETH_ALEN,
+                .ll.sll_addr = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
+        };
+        struct ether_arp arp = {
+                .ea_hdr.ar_hrd = htons(ARPHRD_ETHER), /* HTYPE */
+                .ea_hdr.ar_pro = htons(ETHERTYPE_IP), /* PTYPE */
+                .ea_hdr.ar_hln = ETH_ALEN, /* HLEN */
+                .ea_hdr.ar_pln = sizeof(be32_t), /* PLEN */
+                .ea_hdr.ar_op = htons(ARPOP_REQUEST), /* REQUEST */
+        };
+        int r;
+
+        assert(fd >= 0);
+        assert(pa != 0);
+        assert(ha);
+
+        memcpy(&arp.arp_sha, ha, ETH_ALEN);
+        memcpy(&arp.arp_tpa, &pa, sizeof(pa));
+
+        if (announce)
+                memcpy(&arp.arp_spa, &pa, sizeof(pa));
+
+        r = sendto(fd, &arp, sizeof(struct ether_arp), 0, &link.sa, sizeof(link.ll));
+        if (r < 0)
+                return -errno;
+
+        return 0;
+}
+
+int arp_send_probe(int fd, int ifindex,
+                    be32_t pa, const struct ether_addr *ha) {
+        return arp_send_packet(fd, ifindex, pa, ha, false);
+}
+
+int arp_send_announcement(int fd, int ifindex,
+                          be32_t pa, const struct ether_addr *ha) {
+        return arp_send_packet(fd, ifindex, pa, ha, true);
+}