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net_udp: multicast: multiple improvements
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- support for v4-mapped IPv6 sockets (handled with v4 sockopts in
Linux+Win and v6 sockopts in macOS)
- for mcast4, except of Windows, the interface must be identified by
local address, not device number
- support also setting the bind address directly for v4
- leave mcast4 group with correct ID (not INADDR_ANY)

The local address interface specification was actually the original one
but was removed by the commit 92e24dd (in 2012).
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@MartinPulec
MartinPulec committed Dec 4, 2024
1 parent 65e8bf3 commit d1023bd
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Showing 2 changed files with 180 additions and 18 deletions.
197 changes: 179 additions & 18 deletions src/rtp/net_udp.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,10 @@
#include <pthread.h>
#include <stdalign.h>

#ifndef _WIN32
#include <ifaddrs.h>
#endif

#include "debug.h"
#include "host.h"
#include "memory.h"
Expand All @@ -71,8 +75,11 @@

#define DEFAULT_MAX_UDP_READER_QUEUE_LEN (1920/3*8*1080/1152) //< 10-bit FullHD frame divided by 1280 MTU packets (minus headers)

static unsigned get_ifindex(const char *iface);
static int resolve_address(socket_udp *s, const char *addr, uint16_t tx_port);
static void *udp_reader(void *arg);
static void udp_leave_mcast_grp4(unsigned long addr, int fd,
const char iface[]);

#define IPv4 4
#define IPv6 6
Expand Down Expand Up @@ -167,7 +174,7 @@ struct socket_udp_local {
struct _socket_udp {
struct sockaddr_storage sock;
socklen_t sock_len;
unsigned int ifindex; ///< iface index for multicast
char iface[IF_NAMESIZE]; ///< iface for multicast

struct socket_udp_local *local;
bool local_is_slave; // whether is the local
Expand Down Expand Up @@ -364,16 +371,70 @@ static bool udp_addr_valid4(const char *dst)
return false;
}

static bool udp_join_mcast_grp4(unsigned long addr, int rx_fd, int tx_fd, int ttl, unsigned int ifindex)
/**
* @returns 1. 0 (htonl(INADDR_ANY)) if iface is "";
* 2. representation of the address if iface is an adress
* 3a. [Windows only] interface index
* 3b. [otherwise] iface local address
*/
static in_addr_t
get_iface_local_addr4(const char iface[])
{
if (iface[0] == '\0') {
return htonl(INADDR_ANY);
}

// address specified by bind address
struct in_addr iface_addr;
if (inet_pton(AF_INET, iface, &iface_addr) == 1) {
return iface_addr.s_addr;
}

unsigned int ifindex = get_ifindex(iface);
if (ifindex == (unsigned) -1) {
return htonl(INADDR_ANY);
}

#ifdef _WIN32
// Windows allow the interface specification by ifindex
return htonl(ifindex);
#else
struct ifaddrs *a = NULL;
getifaddrs(&a);
struct ifaddrs *p = a;
while (NULL != p) {
if (p->ifa_addr != NULL && p->ifa_addr->sa_family == AF_INET &&
strcmp(iface, p->ifa_name) == 0) {
struct sockaddr_in *sin = (void *) p->ifa_addr;
in_addr_t ret = sin->sin_addr.s_addr;
freeifaddrs(a);
return ret;
}
p = p->ifa_next;
}
freeifaddrs(a);
MSG(ERROR, "Interface %s has assigned no IPv4 address!\n", iface);
return htonl(INADDR_ANY);
#endif
}

static bool
udp_join_mcast_grp4(unsigned long addr, int rx_fd, int tx_fd, int ttl,
const char iface[])
{
if (IN_MULTICAST(ntohl(addr))) {
#ifndef _WIN32
char loop = 1;
#endif
struct ip_mreq imr;

in_addr_t iface_addr = get_iface_local_addr4(iface);
char buf[IN4_MAX_ASCII_LEN + 1] = "(err. unknown)";
inet_ntop(AF_INET, &iface_addr, buf, sizeof buf);
MSG(INFO, "mcast4 iface bound to: %s\n", buf);

imr.imr_multiaddr.s_addr = addr;
imr.imr_interface.s_addr = ifindex;
imr.imr_interface.s_addr = iface_addr;

if (SETSOCKOPT
(rx_fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, (char *)&imr,
Expand Down Expand Up @@ -401,20 +462,21 @@ static bool udp_join_mcast_grp4(unsigned long addr, int rx_fd, int tx_fd, int tt
}
if (SETSOCKOPT
(tx_fd, IPPROTO_IP, IP_MULTICAST_IF,
(char *)&ifindex, sizeof(ifindex)) != 0) {
(char *) &iface_addr, sizeof iface_addr) != 0) {
socket_error("setsockopt IP_MULTICAST_IF");
return false;
}
}
return true;
}

static void udp_leave_mcast_grp4(unsigned long addr, int fd)
static void
udp_leave_mcast_grp4(unsigned long addr, int fd, const char iface[])
{
if (IN_MULTICAST(ntohl(addr))) {
struct ip_mreq imr;
imr.imr_multiaddr.s_addr = addr;
imr.imr_interface.s_addr = INADDR_ANY;
imr.imr_interface.s_addr = get_iface_local_addr4(iface);
if (SETSOCKOPT
(fd, IPPROTO_IP, IP_DROP_MEMBERSHIP, (char *)&imr,
sizeof(struct ip_mreq)) != 0) {
Expand Down Expand Up @@ -470,16 +532,32 @@ static bool udp_addr_valid6(const char *dst)
return false;
}

static bool udp_join_mcast_grp6(struct in6_addr sin6_addr, int rx_fd, int tx_fd, int ttl, unsigned int ifindex)
static bool
udp_join_mcast_grp6(struct in6_addr sin6_addr, int rx_fd, int tx_fd, int ttl,
const char iface[])
{
#ifdef HAVE_IPv6
// macOS handles v4-mapped addresses transparently as other v6 addrs;
// Linux/Win need to use the v4 sockpts
#ifdef __APPLE__
in_addr_t v4mapped = 0;
memcpy((void *) &v4mapped, sin6_addr.s6_addr + 12, sizeof v4mapped);
if (IN6_IS_ADDR_MULTICAST(&sin6_addr) ||
(IN6_IS_ADDR_V4MAPPED(&sin6_addr) &&
IN_MULTICAST(ntohl(v4mapped)))) {
#else
if (IN6_IS_ADDR_MULTICAST(&sin6_addr)) {
#endif
unsigned int loop = 1;
struct ipv6_mreq imr;
#ifdef MUSICA_IPV6
imr.i6mr_interface = 1;
imr.i6mr_multiaddr = sin6_addr;
#else
unsigned int ifindex = get_ifindex(iface);
if (ifindex == (unsigned) -1) {
return false;
}
imr.ipv6mr_multiaddr = sin6_addr;
imr.ipv6mr_interface = ifindex;
#endif
Expand Down Expand Up @@ -508,28 +586,61 @@ static bool udp_join_mcast_grp6(struct in6_addr sin6_addr, int rx_fd, int tx_fd,
MSG(WARNING, "Using multicast but not setting TTL.\n");
}
if (ifindex != 0) {
#ifdef __APPLE__
MSG(WARNING,
"Interface specification may not work "
"with IPv6 sockets on macOS.\n%s\n",
IN6_IS_ADDR_MULTICAST(&sin6_addr)
? "Please contact us for details or resolution."
: "Use '-4' to enforce IPv4 socket");
#endif
if (SETSOCKOPT(tx_fd, IPPROTO_IPV6, IPV6_MULTICAST_IF,
(char *) &ifindex,
sizeof(ifindex)) != 0) {
socket_error("setsockopt IPV6_MULTICAST_IF");
return false;
}
}

return true;
}
if (IN6_IS_ADDR_V4MAPPED(&sin6_addr)) {
in_addr_t v4mapped = 0;
memcpy((void *) &v4mapped, sin6_addr.s6_addr + 12,
sizeof v4mapped);
return udp_join_mcast_grp4(v4mapped, rx_fd, tx_fd, ttl,
iface);
}

return true;
#else
return false;
#endif
}

static void udp_leave_mcast_grp6(struct in6_addr sin6_addr, int fd, unsigned int ifindex)
static void
udp_leave_mcast_grp6(struct in6_addr sin6_addr, int fd, const char iface[])
{
#ifdef HAVE_IPv6
// see udp_join_mcast_grp for mac/Linux+Win difference
#ifdef __APPLE__
in_addr_t v4mapped = 0;
memcpy((void *) &v4mapped, sin6_addr.s6_addr + 12, sizeof v4mapped);
if (IN6_IS_ADDR_MULTICAST(&sin6_addr) ||
(IN6_IS_ADDR_V4MAPPED(&sin6_addr) &&
IN_MULTICAST(ntohl(v4mapped)))) {
#else
if (IN6_IS_ADDR_MULTICAST(&sin6_addr)) {
#endif
struct ipv6_mreq imr;
#ifdef MUSICA_IPV6
imr.i6mr_interface = 1;
imr.i6mr_multiaddr = sin6_addr;
#else
unsigned int ifindex = get_ifindex(iface);
if (ifindex == (unsigned) -1) {
return;
}
imr.ipv6mr_multiaddr = sin6_addr;
imr.ipv6mr_interface = ifindex;
#endif
Expand All @@ -539,7 +650,13 @@ static void udp_leave_mcast_grp6(struct in6_addr sin6_addr, int fd, unsigned int
sizeof(struct ipv6_mreq)) != 0) {
socket_error("setsockopt IPV6_DROP_MEMBERSHIP");
}
} else if (IN6_IS_ADDR_V4MAPPED(&sin6_addr)) {
in_addr_t v4mapped = 0;
memcpy((void *) &v4mapped, sin6_addr.s6_addr + 12,
sizeof v4mapped);
udp_leave_mcast_grp4(v4mapped, fd, iface);
}

#else
UNUSED(s);
#endif /* HAVE_IPv6 */
Expand Down Expand Up @@ -764,6 +881,47 @@ static bool set_sock_opts_and_bind(fd_t fd, bool ipv6, uint16_t rx_port, int ttl
return true;
}

static unsigned
get_ifindex(const char *iface)
{
if (iface[0] == '\0') {
return 0; // default
}
if (strcmp(iface, "help") == 0) {
printf(
"mcast interface specification can be one of following:\n");
printf( "1. interface name\n");
printf( "2. interface index\n");
printf( "3. bind address (IPv4 only)\n");
printf("\n");
return (unsigned) -1;
}
const unsigned ret = if_nametoindex(iface);
if (ret != 0) {
return ret;
}
// check if the value isn't the index itself
char *endptr = NULL;
const long val = strtol(iface, &endptr, 0);
if (*endptr == '\0' && val >= 0 && (unsigned) val <= UINT_MAX) {
char buf[IF_NAMESIZE];
if (if_indextoname(val, buf) != NULL) {
MSG(INFO, "Using mcast interface %s\n", buf);
return val;
}
}
struct in_addr iface_addr;
if (inet_pton(AF_INET, iface, &iface_addr) == 1) {
error_msg("Interface identified with addres %s not allowed "
"here. Try '-4'...\n",
iface);
return (unsigned) -1;
}
error_msg("Illegal interface specification '%s': %s\n", iface,
ug_strerror(errno));
return (unsigned) -1;
}

ADD_TO_PARAM("udp-queue-len",
"* udp-queue-len=<l>\n"
" Use different queue size than default DEFAULT_MAX_UDP_READER_QUEUE_LEN\n");
Expand Down Expand Up @@ -814,12 +972,7 @@ socket_udp *udp_init_if(const char *addr, const char *iface, uint16_t rx_port,
goto error;
}
if (iface != NULL) {
if ((s->ifindex = if_nametoindex(iface)) == 0) {
error_msg("Illegal interface specification\n");
goto error;
}
} else {
s->ifindex = 0;
snprintf_ch(s->iface, "%s", iface);
}
#ifdef _WIN32
if (!is_host_loopback(addr)) {
Expand Down Expand Up @@ -877,12 +1030,16 @@ socket_udp *udp_init_if(const char *addr, const char *iface, uint16_t rx_port,

switch (s->local->mode) {
case IPv4:
if (!udp_join_mcast_grp4(((struct sockaddr_in *)&s->sock)->sin_addr.s_addr, s->local->rx_fd, s->local->tx_fd, ttl, s->ifindex)) {
if (!udp_join_mcast_grp4(
((struct sockaddr_in *) &s->sock)->sin_addr.s_addr,
s->local->rx_fd, s->local->tx_fd, ttl, s->iface)) {
goto error;
}
break;
case IPv6:
if (!udp_join_mcast_grp6(((struct sockaddr_in6 *)&s->sock)->sin6_addr, s->local->rx_fd, s->local->tx_fd, ttl, s->ifindex)) {
if (!udp_join_mcast_grp6(
((struct sockaddr_in6 *) &s->sock)->sin6_addr,
s->local->rx_fd, s->local->tx_fd, ttl, s->iface)) {
goto error;
}
break;
Expand Down Expand Up @@ -981,10 +1138,14 @@ void udp_exit(socket_udp * s)
}
switch (s->local->mode) {
case IPv4:
udp_leave_mcast_grp4(((struct sockaddr_in *)&s->sock)->sin_addr.s_addr, s->local->rx_fd);
udp_leave_mcast_grp4(
((struct sockaddr_in *) &s->sock)->sin_addr.s_addr,
s->local->rx_fd, s->iface);
break;
case IPv6:
udp_leave_mcast_grp6(((struct sockaddr_in6 *)&s->sock)->sin6_addr, s->local->rx_fd, s->ifindex);
udp_leave_mcast_grp6(
((struct sockaddr_in6 *) &s->sock)->sin6_addr,
s->local->rx_fd, s->iface);
break;
}

Expand Down
1 change: 1 addition & 0 deletions src/utils/net.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@
#endif

enum {
IN4_MAX_ASCII_LEN = 4 * 3 + 3, ///< max len of IPv4 addr str (w/o '\0')
/// maximal length of textual representation of IPv6 address including
/// eventual scope ID but without terminating NUL byte
IN6_MAX_ASCII_LEN = 40 /* 32 nibbles + 7 colons + "%" */ + IF_NAMESIZE,
Expand Down

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