diff options
Diffstat (limited to 'networking/udhcp/arpping.c')
| -rw-r--r-- | networking/udhcp/arpping.c | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/networking/udhcp/arpping.c b/networking/udhcp/arpping.c new file mode 100644 index 0000000..e0710dc --- /dev/null +++ b/networking/udhcp/arpping.c @@ -0,0 +1,116 @@ +/* vi: set sw=4 ts=4: */ +/* + * arpping.c + * + * Mostly stolen from: dhcpcd - DHCP client daemon + * by Yoichi Hariguchi <yoichi@fore.com> + */ + +#include <netinet/if_ether.h> +#include <net/if_arp.h> + +#include "common.h" +#include "dhcpd.h" + + +struct arpMsg { + /* Ethernet header */ + uint8_t h_dest[6]; /* 00 destination ether addr */ + uint8_t h_source[6]; /* 06 source ether addr */ + uint16_t h_proto; /* 0c packet type ID field */ + + /* ARP packet */ + uint16_t htype; /* 0e hardware type (must be ARPHRD_ETHER) */ + uint16_t ptype; /* 10 protocol type (must be ETH_P_IP) */ + uint8_t hlen; /* 12 hardware address length (must be 6) */ + uint8_t plen; /* 13 protocol address length (must be 4) */ + uint16_t operation; /* 14 ARP opcode */ + uint8_t sHaddr[6]; /* 16 sender's hardware address */ + uint8_t sInaddr[4]; /* 1c sender's IP address */ + uint8_t tHaddr[6]; /* 20 target's hardware address */ + uint8_t tInaddr[4]; /* 26 target's IP address */ + uint8_t pad[18]; /* 2a pad for min. ethernet payload (60 bytes) */ +} PACKED; + +enum { + ARP_MSG_SIZE = 0x2a +}; + + +/* Returns 1 if no reply received */ + +int FAST_FUNC arpping(uint32_t test_ip, uint32_t from_ip, uint8_t *from_mac, const char *interface) +{ + int timeout_ms; + struct pollfd pfd[1]; +#define s (pfd[0].fd) /* socket */ + int rv = 1; /* "no reply received" yet */ + struct sockaddr addr; /* for interface name */ + struct arpMsg arp; + + s = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)); + if (s == -1) { + bb_perror_msg(bb_msg_can_not_create_raw_socket); + return -1; + } + + if (setsockopt_broadcast(s) == -1) { + bb_perror_msg("cannot enable bcast on raw socket"); + goto ret; + } + + /* send arp request */ + memset(&arp, 0, sizeof(arp)); + memset(arp.h_dest, 0xff, 6); /* MAC DA */ + memcpy(arp.h_source, from_mac, 6); /* MAC SA */ + arp.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */ + arp.htype = htons(ARPHRD_ETHER); /* hardware type */ + arp.ptype = htons(ETH_P_IP); /* protocol type (ARP message) */ + arp.hlen = 6; /* hardware address length */ + arp.plen = 4; /* protocol address length */ + arp.operation = htons(ARPOP_REQUEST); /* ARP op code */ + memcpy(arp.sHaddr, from_mac, 6); /* source hardware address */ + memcpy(arp.sInaddr, &from_ip, sizeof(from_ip)); /* source IP address */ + /* tHaddr is zero-fiiled */ /* target hardware address */ + memcpy(arp.tInaddr, &test_ip, sizeof(test_ip)); /* target IP address */ + + memset(&addr, 0, sizeof(addr)); + safe_strncpy(addr.sa_data, interface, sizeof(addr.sa_data)); + if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0) { + // TODO: error message? caller didn't expect us to fail, + // just returning 1 "no reply received" misleads it. + goto ret; + } + + /* wait for arp reply, and check it */ + timeout_ms = 2000; + do { + int r; + unsigned prevTime = monotonic_us(); + + pfd[0].events = POLLIN; + r = safe_poll(pfd, 1, timeout_ms); + if (r < 0) + break; + if (r) { + r = read(s, &arp, sizeof(arp)); + if (r < 0) + break; + if (r >= ARP_MSG_SIZE + && arp.operation == htons(ARPOP_REPLY) + /* don't check it: Linux doesn't return proper tHaddr (fixed in 2.6.24?) */ + /* && memcmp(arp.tHaddr, from_mac, 6) == 0 */ + && *((uint32_t *) arp.sInaddr) == test_ip + ) { + rv = 0; + break; + } + } + timeout_ms -= ((unsigned)monotonic_us() - prevTime) / 1000; + } while (timeout_ms > 0); + + ret: + close(s); + DEBUG("%srp reply received for this address", rv ? "No a" : "A"); + return rv; +} |