The following information is partly extracted from RFC3549 (ftp://ftp.rfc-editor.org/in-notes/rfc3549.txt)
NLM_F_MULTI
Netlink header flag set, except for the last header which has the Netlink header type NLMSG_DONE
.0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Process ID (PID) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
<------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) ---> +----------------------------+- - -+- - - - - - - - - - -+- - -+ | Header | Pad | Payload | Pad | | struct nlmsghdr | | | | +----------------------------+- - -+- - - - - - - - - - -+- - -+
<--- nlmsg_total_size(payload) ---> <-- nlmsg_msg_size(payload) -> +----------+- - -+-------------+- - -+-------- - - | nlmsghdr | Pad | Payload | Pad | nlmsghdr +----------+- - -+-------------+- - -+-------- - - nlmsg_data(nlh)---^ ^ nlmsg_next(nlh)-----------------------+
<---------------------- nlmsg_len(nlh) ---------------------> <------ hdrlen ------> <- nlmsg_attrlen(nlh, hdrlen) -> +----------------------+- - -+--------------------------------+ | Family Header | Pad | Attributes | +----------------------+- - -+--------------------------------+ nlmsg_attrdata(nlh, hdrlen)---^
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Netlink message header | | type = NLMSG_ERROR | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Error code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OLD Netlink message header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// The most common way to start creating a message is by providing an // defined netlink header to nlmsg_build(): struct nlmsghdr hdr = { .nlmsg_type = MY_TYPE, .nlmsg_flags = MY_FLAGS, }; struct nl_msg *msg = nlmsg_build(&hdr); // For simple usages where only the message type and flags is of // interenst a shortcut can be taken: struct nl_msg *msg = nlmsg_build_simple(MY_TYPE, MY_FLAGS); // When using a headerless message for creating nested attributes // the header is not required and nlmsg_build_no_hdr() may be used: struct nl_msg *msg = nlmsg_build_no_hdr(); // The header can later be retrieved with nlmsg_hdr() and changed again: nlmsg_hdr(msg)->nlmsg_flags |= YET_ANOTHER_FLAG;
// Payload may be added to the message via nlmsg_append(). The fourth // parameter specifies whether to pad up to NLMSG_ALIGN to make sure // that a possible further data block is properly aligned. nlmsg_append(msg, &mydata, sizeof(mydata), 0);
// After successful use of the message, the memory must be freed // using nlmsg_free() nlmsg_free(msg);
int n; unsigned char *buf; struct nlmsghdr *hdr; n = nl_recv(handle, NULL, &buf); hdr = (struct nlmsghdr *) buf; while (nlmsg_ok(hdr, n)) { // Process message here... hdr = nlmsg_next(hdr, &n); }
Data Structures | |
struct | nlmsghdr |
Netlink message header. More... | |
struct | nlmsgerr |
Netlink error message. More... | |
Netlink Message Type Translations | |
char * | nl_nlmsgtype2str (int type, char *buf, size_t size) |
Convert netlink message type number to character string. | |
int | nl_str2nlmsgtype (const char *name) |
Convert character string to netlink message type. | |
Size Calculations | |
int | nlmsg_msg_size (int payload) |
length of netlink message not including padding | |
int | nlmsg_total_size (int payload) |
length of netlink message including padding | |
int | nlmsg_padlen (int payload) |
length of padding at the message's tail | |
Payload Access | |
void * | nlmsg_data (const struct nlmsghdr *nlh) |
head of message payload | |
void * | nlmsg_tail (const struct nlmsghdr *nlh) |
head of message payload | |
int | nlmsg_len (const struct nlmsghdr *nlh) |
length of message payload | |
Attribute Access | |
nlattr * | nlmsg_attrdata (const struct nlmsghdr *nlh, int hdrlen) |
head of attributes data | |
int | nlmsg_attrlen (const struct nlmsghdr *nlh, int hdrlen) |
length of attributes data | |
Message Parsing | |
int | nlmsg_ok (const struct nlmsghdr *nlh, int remaining) |
check if the netlink message fits into the remaining bytes | |
nlmsghdr * | nlmsg_next (struct nlmsghdr *nlh, int *remaining) |
next netlink message in message stream | |
int | nlmsg_parse (struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[], int maxtype, struct nla_policy *policy) |
parse attributes of a netlink message | |
nlattr * | nlmsg_find_attr (struct nlmsghdr *nlh, int hdrlen, int attrtype) |
nlmsg_find_attr - find a specific attribute in a netlink message | |
int | nlmsg_validate (struct nlmsghdr *nlh, int hdrlen, int maxtype, struct nla_policy *policy) |
nlmsg_validate - validate a netlink message including attributes | |
Message Building/Access | |
nl_msg * | nlmsg_new (void) |
nl_msg * | nlmsg_build (struct nlmsghdr *hdr) |
Build a new netlink message. | |
nl_msg * | nlmsg_build_simple (int nlmsgtype, int flags) |
nl_msg * | nlmsg_build_no_hdr (void) |
nl_msg * | nlmsg_convert (struct nlmsghdr *hdr) |
int | nlmsg_append (struct nl_msg *n, void *data, size_t len, int pad) |
Append raw data to a netlink message. | |
nlmsghdr * | nlmsg_put (struct nl_msg *n, uint32_t pid, uint32_t seq, int type, int payload, int flags) |
nlmsg_put - Add a netlink message header | |
nlmsghdr * | nlmsg_hdr (struct nl_msg *n) |
Return actual netlink message. | |
void | nlmsg_free (struct nl_msg *n) |
Free a netlink message. | |
Attribute Modification | |
void | nlmsg_set_proto (struct nl_msg *msg, int protocol) |
int | nlmsg_get_proto (struct nl_msg *msg) |
void | nlmsg_set_src (struct nl_msg *msg, struct sockaddr_nl *addr) |
sockaddr_nl * | nlmsg_get_src (struct nl_msg *msg) |
void | nlmsg_set_dst (struct nl_msg *msg, struct sockaddr_nl *addr) |
sockaddr_nl * | nlmsg_get_dst (struct nl_msg *msg) |
void | nlmsg_set_creds (struct nl_msg *msg, struct ucred *creds) |
ucred * | nlmsg_get_creds (struct nl_msg *msg) |
Netlink Message Flags Translations | |
char * | nl_nlmsg_flags2str (int flags, char *buf, size_t len) |
Translate netlink message flags into a character string (Reentrant). | |
Direct Parsing | |
int | nl_msg_parse (struct nl_msg *msg, void(*cb)(struct nl_object *, void *), void *arg) |
Iterators | |
#define | nlmsg_for_each_attr(pos, nlh, hdrlen, rem) |
Iterate over a stream of attributes in a message. | |
#define | nlmsg_for_each_msg(pos, head, len, rem) |
Iterate over a stream of messages. | |
Standard message flags | |
#define | NLM_F_REQUEST 1 |
Must be set on all request messages (typically from user space to kernel space). | |
#define | NLM_F_MULTI 2 |
Indicates the message is part of a multipart message terminated by NLMSG_DONE. | |
#define | NLM_F_ACK 4 |
Request for an acknowledgment on success. | |
#define | NLM_F_ECHO 8 |
Echo this request. | |
Additional message flags for GET requests | |
#define | NLM_F_ROOT 0x100 |
Return the complete table instead of a single entry. | |
#define | NLM_F_MATCH 0x200 |
Return all entries matching criteria passed in message content. | |
#define | NLM_F_ATOMIC 0x400 |
Return an atomic snapshot of the table being referenced. | |
#define | NLM_F_DUMP (NLM_F_ROOT|NLM_F_MATCH) |
Dump all entries. | |
Additional messsage flags for NEW requests | |
#define | NLM_F_REPLACE 0x100 |
Replace existing matching config object with this request. | |
#define | NLM_F_EXCL 0x200 |
Don't replace the config object if it already exists. | |
#define | NLM_F_CREATE 0x400 |
Create config object if it doesn't already exist. | |
#define | NLM_F_APPEND 0x800 |
Add to the end of the object list. | |
Standard Message types | |
#define | NLMSG_NOOP 0x1 |
No operation, message must be ignored. | |
#define | NLMSG_ERROR 0x2 |
The message signals an error and the payload contains a nlmsgerr structure. | |
#define | NLMSG_DONE 0x3 |
Message terminates a multipart message. | |
#define | NLMSG_OVERRUN 0x4 |
The message signals that data got lost. | |
#define | NLMSG_MIN_TYPE 0x10 |
Lower limit of reserved message types. |
#define nlmsg_for_each_attr | ( | pos, | |||
nlh, | |||||
hdrlen, | |||||
rem | ) |
Value:
nla_for_each_attr(pos, nlmsg_attrdata(nlh, hdrlen), \ nlmsg_attrlen(nlh, hdrlen), rem)
pos | loop counter, set to current attribute | |
nlh | netlink message header | |
hdrlen | length of family header | |
rem | initialized to len, holds bytes currently remaining in stream |
#define NLM_F_REQUEST 1 |
Must be set on all request messages (typically from user space to kernel space).
Definition at line 86 of file netlink-kernel.h.
Referenced by nl_send_auto_complete().
#define NLM_F_ROOT 0x100 |
Return the complete table instead of a single entry.
Definition at line 115 of file netlink-kernel.h.
#define NLM_F_REPLACE 0x100 |
Replace existing matching config object with this request.
Definition at line 145 of file netlink-kernel.h.
Referenced by rtnl_cls_build_change_request(), rtnl_neigh_build_change_request(), and rtnl_qdisc_build_change_request().
#define NLMSG_NOOP 0x1 |
No operation, message must be ignored.
Definition at line 177 of file netlink-kernel.h.
Referenced by nl_recvmsgs().
#define nlmsg_for_each_msg | ( | pos, | |||
head, | |||||
len, | |||||
rem | ) |
Value:
for (pos = head, rem = len; \ nlmsg_ok(pos, rem); \ pos = nlmsg_next(pos, &(rem)))
pos | loop counter, set to current message | |
head | head of message stream | |
len | length of message stream | |
rem | initialized to len, holds bytes currently remaining in stream |
#define NLM_F_MULTI 2 |
Indicates the message is part of a multipart message terminated by NLMSG_DONE.
Definition at line 92 of file netlink-kernel.h.
#define NLM_F_ACK 4 |
Request for an acknowledgment on success.
Definition at line 97 of file netlink-kernel.h.
Referenced by nl_recvmsgs(), and nl_send_auto_complete().
#define NLM_F_ECHO 8 |
#define NLM_F_MATCH 0x200 |
Return all entries matching criteria passed in message content.
Definition at line 120 of file netlink-kernel.h.
#define NLM_F_ATOMIC 0x400 |
Return an atomic snapshot of the table being referenced.
This may require special privileges because it has the potential to interrupt service in the FE for a longer time.
Definition at line 127 of file netlink-kernel.h.
#define NLM_F_DUMP (NLM_F_ROOT|NLM_F_MATCH) |
#define NLM_F_EXCL 0x200 |
Don't replace the config object if it already exists.
Definition at line 150 of file netlink-kernel.h.
#define NLM_F_CREATE 0x400 |
Create config object if it doesn't already exist.
Definition at line 155 of file netlink-kernel.h.
Referenced by rtnl_addr_build_add_request(), rtnl_class_build_add_request(), rtnl_cls_build_add_request(), rtnl_neigh_build_add_request(), rtnl_qdisc_build_add_request(), rtnl_route_build_add_request(), and rtnl_rule_build_add_request().
#define NLM_F_APPEND 0x800 |
#define NLMSG_ERROR 0x2 |
The message signals an error and the payload contains a nlmsgerr structure.
This can be looked at as a NACK and typically it is from FEC to CPC.
Definition at line 184 of file netlink-kernel.h.
Referenced by nl_recvmsgs().
#define NLMSG_DONE 0x3 |
Message terminates a multipart message.
Definition at line 189 of file netlink-kernel.h.
Referenced by nl_recvmsgs().
#define NLMSG_OVERRUN 0x4 |
The message signals that data got lost.
Definition at line 194 of file netlink-kernel.h.
Referenced by nl_recvmsgs().
#define NLMSG_MIN_TYPE 0x10 |
int nlmsg_msg_size | ( | int | payload | ) |
length of netlink message not including padding
payload | length of message payload |
Definition at line 166 of file msg.c.
Referenced by nl_recvmsgs(), nl_send_simple(), nlmsg_new(), nlmsg_padlen(), nlmsg_parse(), nlmsg_put(), nlmsg_total_size(), and nlmsg_validate().
int nlmsg_total_size | ( | int | payload | ) |
length of netlink message including padding
payload | length of message payload |
Definition at line 175 of file msg.c.
References nlmsg_msg_size().
Referenced by nlmsg_padlen().
int nlmsg_padlen | ( | int | payload | ) |
length of padding at the message's tail
payload | length of message payload |
Definition at line 184 of file msg.c.
References nlmsg_msg_size(), and nlmsg_total_size().
Referenced by nlmsg_put().
void* nlmsg_data | ( | const struct nlmsghdr * | nlh | ) |
head of message payload
nlh | netlink messsage header |
Definition at line 200 of file msg.c.
Referenced by nl_recvmsgs(), nla_put_nested(), nlmsg_attrdata(), and nlmsg_put().
void* nlmsg_tail | ( | const struct nlmsghdr * | nlh | ) |
head of message payload
nlh | netlink messsage header |
Definition at line 205 of file msg.c.
References nlmsghdr::nlmsg_len.
Referenced by nla_nest_end(), nla_nest_start(), and nla_reserve().
int nlmsg_len | ( | const struct nlmsghdr * | nlh | ) |
length of message payload
nlh | netlink message header |
Definition at line 214 of file msg.c.
References nlmsghdr::nlmsg_len.
Referenced by nla_put_nested(), and nlmsg_attrlen().
head of attributes data
nlh | netlink message header | |
hdrlen | length of family specific header |
Definition at line 231 of file msg.c.
References nlmsg_data().
Referenced by nlmsg_find_attr(), nlmsg_parse(), and nlmsg_validate().
int nlmsg_attrlen | ( | const struct nlmsghdr * | nlh, | |
int | hdrlen | |||
) |
length of attributes data
nlh | netlink message header | |
hdrlen | length of family specific header |
Definition at line 242 of file msg.c.
References nlmsg_len().
Referenced by nlmsg_find_attr(), nlmsg_parse(), and nlmsg_validate().
int nlmsg_ok | ( | const struct nlmsghdr * | nlh, | |
int | remaining | |||
) |
check if the netlink message fits into the remaining bytes
nlh | netlink message header | |
remaining | number of bytes remaining in message stream |
Definition at line 259 of file msg.c.
References nlmsghdr::nlmsg_len.
Referenced by nl_recvmsgs().
next netlink message in message stream
nlh | netlink message header | |
remaining | number of bytes remaining in message stream |
Definition at line 274 of file msg.c.
References nlmsghdr::nlmsg_len.
Referenced by nl_recvmsgs().
int nlmsg_parse | ( | struct nlmsghdr * | nlh, | |
int | hdrlen, | |||
struct nlattr * | tb[], | |||
int | maxtype, | |||
struct nla_policy * | policy | |||
) |
parse attributes of a netlink message
nlh | netlink message header | |
hdrlen | length of family specific header | |
tb | destination array with maxtype+1 elements | |
maxtype | maximum attribute type to be expected | |
policy | validation policy |
Definition at line 293 of file msg.c.
References nla_parse(), nlmsg_attrdata(), nlmsg_attrlen(), nlmsghdr::nlmsg_len, and nlmsg_msg_size().
nlmsg_find_attr - find a specific attribute in a netlink message
nlh | netlink message header | |
hdrlen | length of familiy specific header | |
attrtype | type of attribute to look for |
Definition at line 311 of file msg.c.
References nla_find(), nlmsg_attrdata(), and nlmsg_attrlen().
int nlmsg_validate | ( | struct nlmsghdr * | nlh, | |
int | hdrlen, | |||
int | maxtype, | |||
struct nla_policy * | policy | |||
) |
nlmsg_validate - validate a netlink message including attributes
nlh | netlinket message header | |
hdrlen | length of familiy specific header | |
maxtype | maximum attribute type to be expected | |
policy | validation policy |
Definition at line 324 of file msg.c.
References nla_validate(), nlmsg_attrdata(), nlmsg_attrlen(), nlmsghdr::nlmsg_len, and nlmsg_msg_size().
struct nl_msg* nlmsg_build | ( | struct nlmsghdr * | hdr | ) |
Build a new netlink message.
hdr | Netlink message header template |
Definition at line 373 of file msg.c.
References nlmsg_new().
Referenced by nl_send_simple(), nlmsg_build_no_hdr(), nlmsg_build_simple(), and rtnl_neightbl_build_change_request().
int nlmsg_append | ( | struct nl_msg * | n, | |
void * | data, | |||
size_t | len, | |||
int | pad | |||
) |
Append raw data to a netlink message.
n | netlink message | |
data | data to add | |
len | length of data | |
pad | add padding at the end? |
Definition at line 441 of file msg.c.
Referenced by flnl_lookup_build_request(), nl_send_simple(), rtnl_link_build_change_request(), rtnl_neightbl_build_change_request(), and rtnl_qdisc_build_delete_request().
struct nlmsghdr* nlmsg_put | ( | struct nl_msg * | n, | |
uint32_t | pid, | |||
uint32_t | seq, | |||
int | type, | |||
int | payload, | |||
int | flags | |||
) |
nlmsg_put - Add a netlink message header
n | netlink message | |
pid | netlink process id | |
seq | sequence number of message | |
type | message type | |
payload | length of message payload | |
flags | message flags |
Definition at line 469 of file msg.c.
References nlmsg_data(), nlmsghdr::nlmsg_flags, nlmsghdr::nlmsg_len, nlmsg_msg_size(), nlmsg_padlen(), nlmsghdr::nlmsg_pid, nlmsghdr::nlmsg_seq, and nlmsghdr::nlmsg_type.
struct nlmsghdr* nlmsg_hdr | ( | struct nl_msg * | n | ) |
Return actual netlink message.
n | netlink message |
Definition at line 499 of file msg.c.
Referenced by nl_cache_parse_and_add(), nl_msg_parse(), nl_send_auto_complete(), and nl_sendmsg().
void nlmsg_free | ( | struct nl_msg * | n | ) |
Free a netlink message.
n | netlink message |
Definition at line 512 of file msg.c.
Referenced by flnl_lookup(), flnl_lookup_build_request(), nl_recvmsgs(), nl_send_simple(), rtnl_addr_add(), rtnl_addr_delete(), rtnl_class_add(), rtnl_cls_add(), rtnl_cls_change(), rtnl_cls_delete(), rtnl_link_build_change_request(), rtnl_link_change(), rtnl_neigh_add(), rtnl_neigh_change(), rtnl_neigh_delete(), rtnl_neightbl_build_change_request(), rtnl_neightbl_change(), rtnl_qdisc_add(), rtnl_qdisc_change(), rtnl_qdisc_delete(), rtnl_rule_add(), and rtnl_rule_delete().
char* nl_nlmsgtype2str | ( | int | type, | |
char * | buf, | |||
size_t | size | |||
) |
Convert netlink message type number to character string.
type | Netlink message type. | |
buf | Destination buffer. | |
size | Size of destination buffer. |
int nl_str2nlmsgtype | ( | const char * | name | ) |
Convert character string to netlink message type.
name | Name of netlink message type. |
char* nl_nlmsg_flags2str | ( | int | flags, | |
char * | buf, | |||
size_t | len | |||
) |
Translate netlink message flags into a character string (Reentrant).
flags | netlink message flags | |
buf | destination buffer | |
len | buffer length |