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sock.c
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sock.c
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#include "mai.h"
/* ######################################################################## */
static const char *if_name; // multicast interface name
static uint8_t if_local[10]; // multicast interface l2 address
static unsigned int if_mtu; // multicast interface mtu
static int if_index; // multicast interface index
static struct in_addr if_addr; // multicast interface address
/* ######################################################################## */
static inline int setsockopt_i(int sk, int level, int name, int value) {
int opt = value;
return(setsockopt(sk, level, name, &opt, sizeof(opt)));
}
/* ######################################################################## */
static int sock_send(const char *ip, const uint16_t port) {
// convert target address
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
if (!inet_aton(ip, &addr.sin_addr))
return(mai_error("target address (%s): %m\n", ip));
// create udp4 socket
int sk;
if ((sk = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
return(mai_error("socket: %m\n"));
// set outbound multicast interface
if (if_name && setsockopt(sk, IPPROTO_IP, IP_MULTICAST_IF, &if_addr, sizeof(if_addr)))
return(mai_error("multicast interface: %m\n"));
// set type of service (equivalent to DSCP AF41)
if (setsockopt_i(sk, IPPROTO_IP, IP_TOS, IPTOS_PREC_FLASHOVERRIDE|IPTOS_THROUGHPUT))
return(mai_error("ip tos: %m\n"));
// set time to live
if (setsockopt_i(sk, IPPROTO_IP, IP_MULTICAST_TTL, 32))
return(mai_error("multicast ttl: %m\n"));
// set default send address
if (connect(sk, (struct sockaddr *)&addr, sizeof(addr)))
return(mai_error("connect: %m\n"));
return(sk);
}
/* ######################################################################## */
static int sock_recv(const char *ip, const uint16_t port) {
// setup multicast group request
struct ip_mreqn req = (struct ip_mreqn){ .imr_ifindex = if_index, .imr_address.s_addr = htonl(INADDR_ANY) };
if (!inet_aton(ip, &req.imr_multiaddr))
return(mai_error("multicast address (%s): %m.\n", ip));
// create udp4 socket
int sk;
if ((sk = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
return(mai_error("create socket: %m.\n"));
// join multicast group to start receving packets
if (setsockopt(sk, IPPROTO_IP, IP_ADD_MEMBERSHIP, &req, sizeof(req)))
return(mai_error("ip add membership: %m\n"));
// let other processes bind to same port
if (setsockopt_i(sk, SOL_SOCKET, SO_REUSEPORT, 1))
return(mai_error("reuse port: %m\n"));
// let other processes bind to same address
if (setsockopt_i(sk, SOL_SOCKET, SO_REUSEADDR, 1))
return(mai_error("reuse address: %m\n"));
// bind to port and multicast destination
struct sockaddr_in addr;
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr = req.imr_multiaddr;
if (bind(sk, (struct sockaddr *)&addr, sizeof(addr)))
return(mai_error("bind: %m\n"));
// finished, success
return(sk);
}
/* ######################################################################## */
int mai_sock_open(int mode, const char *ip, const uint16_t port) {
return((mode == 's') ? sock_send(ip, port) : sock_recv(ip, port));
}
/* ######################################################################## */
int mai_sock_if_set(const char *name) {
if (!name || !name[0])
return(0);
if ((if_name = strdup(name)) == NULL)
return(mai_error("strdup: %m\n"));
int sk;
if ((sk = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
return(mai_error("socket: %m\n"));
// setup interface request
struct ifreq ifr;
strncpy(ifr.ifr_name, if_name, IFNAMSIZ);
ifr.ifr_name[IFNAMSIZ-1] = 0;
// ask for interface mtu
if (ioctl(sk, SIOCGIFMTU, &ifr))
return(mai_error("get interface mtu (%s): %m\n", if_name));
if_mtu = ifr.ifr_mtu;
// ask for interface index
if (ioctl(sk, SIOCGIFINDEX, &ifr))
return(mai_error("get interface index (%s): %m\n", if_name));
if_index = ifr.ifr_ifindex;
// ask for primary ipv4 address
ifr.ifr_addr.sa_family = AF_INET;
if (ioctl(sk, SIOCGIFADDR, &ifr))
return(mai_error("get interface address (%s): %m\n", if_name));
if_addr = ((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr;
// ask for layer2 address
if (ioctl(sk, SIOCGIFHWADDR, &ifr))
return(mai_error("get interface hardware address (%s): %m\n", if_name));
uint8_t *out = &if_local[0];
*out++ = ifr.ifr_hwaddr.sa_data[0];
*out++ = ifr.ifr_hwaddr.sa_data[1];
*out++ = ifr.ifr_hwaddr.sa_data[2];
*out++ = 0xFF;
*out++ = 0xFE;
*out++ = ifr.ifr_hwaddr.sa_data[3];
*out++ = ifr.ifr_hwaddr.sa_data[4];
*out++ = ifr.ifr_hwaddr.sa_data[5];
*out++ = 0x00;
*out++ = 0x02;
close(sk);
return(0);
}
/* ######################################################################## */
size_t mai_sock_if_mtu(void) { return( if_mtu); }
const void *mai_sock_if_addr(void) { return(&if_addr); }
const char *mai_sock_if_name(void) { return( if_name); }
void mai_sock_if_local(uint8_t *out) { memcpy(out, if_local, sizeof(if_local)); }
/* ######################################################################## */