---
name: "getifmaddrs"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd", "macos"]
url: "https://new.carta.tech/freeifmaddrs"
---

# getifmaddrs(3)

get multicast group memberships

Part of [freeifmaddrs(3)](/freeifmaddrs/3.md).

## NAME

**getifmaddrs** – get multicast group memberships

## SYNOPSIS

**#include \<ifaddrs.h\>**

*int*\

**getifmaddrs**(*struct ifmaddrs \*\*ifmap*);

*void*\

**freeifmaddrs**(*struct ifmaddrs \*ifmp*);

## DESCRIPTION

The **getifmaddrs**() function stores a reference to a linked list of the multicast memberships on the local machine in the memory referenced by *ifmap*. The list consists of *ifmaddrs* structures, as defined in the include file ⟨ifaddrs.h⟩. The *ifmaddrs* structure contains at least the following entries:

```
    struct ifmaddrs   *ifma_next;     /* Pointer to next struct */
    struct sockaddr   *ifma_name;     /* Interface name (AF_LINK) */
    struct sockaddr   *ifma_addr;     /* Multicast address */
    struct sockaddr   *ifma_lladdr;   /* Link-layer translation, if any */
```

The *ifma\_next* field contains a pointer to the next structure on the list. This field is NULL in last structure on the list.

The *ifma\_name* field references an AF\_LINK address structure, containing the name of the interface where the membership exists.

The *ifma\_addr* references the address that this membership is for.

The *ifma\_lladdr* field references a link-layer translation for the protocol-level address in *ifma\_addr*, if one is set, otherwise it is NULL.

The data returned by **getifmaddrs**() is dynamically allocated and should be freed using **freeifmaddrs**() when no longer needed.

## RETURN VALUES

The **getifmaddrs()** function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

## ERRORS

The **getifmaddrs**() may fail and set *errno* for any of the errors specified for the library routines [malloc(3)](/malloc/3.md) or [sysctl(3)](/sysctl/3.md).

## SEE ALSO

[sysctl(3)](/sysctl/3.md), [networking(4)](/networking/4.md), [ifconfig(8)](/ifconfig/8.md)

## HISTORY

The **getifmaddrs**() function first appeared in FreeBSD 5.2.

## BUGS

If both ⟨net/if.h⟩ and ⟨ifaddrs.h⟩ are being included, ⟨net/if.h⟩ *must* be included before ⟨ifaddrs.h⟩.