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| .TH PCAP_FINDALLDEVS 3PCAP "22 August 2010" |
| .SH NAME |
| pcap_findalldevs, pcap_freealldevs \- get a list of capture devices, and |
| free that list |
| .SH SYNOPSIS |
| .nf |
| .ft B |
| #include <pcap/pcap.h> |
| .ft |
| .LP |
| .nf |
| .ft B |
| char errbuf[PCAP_ERRBUF_SIZE]; |
| .ft |
| .LP |
| .ft B |
| int pcap_findalldevs(pcap_if_t **alldevsp, char *errbuf); |
| void pcap_freealldevs(pcap_if_t *alldevs); |
| .ft |
| .fi |
| .SH DESCRIPTION |
| .B pcap_findalldevs() |
| constructs a list of network devices that can be opened with |
| .B pcap_create() |
| and |
| .B pcap_activate() |
| or with |
| .BR pcap_open_live() . |
| (Note that there may be network devices that cannot be opened by the |
| process calling |
| .BR pcap_findalldevs() , |
| because, for example, that process does not have sufficient privileges |
| to open them for capturing; if so, those devices will not appear on the |
| list.) |
| If |
| .B pcap_findalldevs() |
| succeeds, the pointer pointed to by |
| .I alldevsp |
| is set to point to the first element of the list, or to |
| .B NULL |
| if no devices were found (this is considered success). |
| Each element of the list is of type |
| .BR pcap_if_t , |
| and has the following members: |
| .RS |
| .TP |
| .B next |
| if not |
| .BR NULL , |
| a pointer to the next element in the list; |
| .B NULL |
| for the last element of the list |
| .TP |
| .B name |
| a pointer to a string giving a name for the device to pass to |
| .B pcap_open_live() |
| .TP |
| .B description |
| if not |
| .BR NULL , |
| a pointer to a string giving a human-readable description of the device |
| .TP |
| .B addresses |
| a pointer to the first element of a list of network addresses for the |
| device, |
| or |
| .B NULL |
| if the device has no addresses |
| .TP |
| .B flags |
| device flags: |
| .RS |
| .TP |
| .B PCAP_IF_LOOPBACK |
| set if the device is a loopback interface |
| .RE |
| .RE |
| .PP |
| Each element of the list of addresses is of type |
| .BR pcap_addr_t , |
| and has the following members: |
| .RS |
| .TP |
| .B next |
| if not |
| .BR NULL , |
| a pointer to the next element in the list; |
| .B NULL |
| for the last element of the list |
| .TP |
| .B addr |
| a pointer to a |
| .B "struct sockaddr" |
| containing an address |
| .TP |
| .B netmask |
| if not |
| .BR NULL , |
| a pointer to a |
| .B "struct sockaddr" |
| that contains the netmask corresponding to the address pointed to by |
| .B addr |
| .TP |
| .B broadaddr |
| if not |
| .BR NULL , |
| a pointer to a |
| .B "struct sockaddr" |
| that contains the broadcast address corresponding to the address pointed |
| to by |
| .BR addr ; |
| may be null if the device doesn't support broadcasts |
| .TP |
| .B dstaddr |
| if not |
| .BR NULL , |
| a pointer to a |
| .B "struct sockaddr" |
| that contains the destination address corresponding to the address pointed |
| to by |
| .BR addr ; |
| may be null if the device isn't a point-to-point interface |
| .RE |
| .PP |
| Note that the addresses in the list of addresses might be IPv4 |
| addresses, IPv6 addresses, or some other type of addresses, so you must |
| check the |
| .B sa_family |
| member of the |
| .B "struct sockaddr" |
| before interpreting the contents of the address; do not assume that the |
| addresses are all IPv4 addresses, or even all IPv4 or IPv6 addresses. |
| IPv4 addresses have the value |
| .BR AF_INET , |
| IPv6 addresses have the value |
| .B AF_INET6 |
| (which older operating systems that don't support IPv6 might not |
| define), and other addresses have other values. Whether other addresses |
| are returned, and what types they might have is platform-dependent. |
| For IPv4 addresses, the |
| .B "struct sockaddr" |
| pointer can be interpreted as if it pointed to a |
| .BR "struct sockaddr_in" ; |
| for IPv6 addresses, it can be interpreted as if it pointed to a |
| .BR "struct sockaddr_in6". |
| .PP |
| The list of devices must be freed with |
| .BR pcap_freealldevs() , |
| whch frees the list pointed to by |
| .IR alldevs . |
| .SH RETURN VALUE |
| .B pcap_findalldevs() |
| returns 0 on success and \-1 on failure; as indicated, finding no |
| devices is considered success, rather than failure, so 0 will be |
| returned in that case. |
| If \-1 is returned, |
| .I errbuf |
| is filled in with an appropriate error message. |
| .I errbuf |
| is assumed to be able to hold at least |
| .B PCAP_ERRBUF_SIZE |
| chars. |
| .SH SEE ALSO |
| pcap(3PCAP), pcap_create(3PCAP), pcap_activate(3PCAP), |
| pcap_open_live(3PCAP) |