proc_net - network layer information - man(5) - [phpMan]

Che Dong

proc_pid_net(5) File Formats Manual proc_pid_net(5)

NAME
/proc/pid/net/, /proc/net/ - network layer information

DESCRIPTION
/proc/pid/net/ (since Linux 2.6.25)
See the description of /proc/net.

/proc/net/
This directory contains various files and subdirectories containing information about
the networking layer. The files contain ASCII structures and are, therefore, readable
with cat(1). However, the standard netstat(8) suite provides much cleaner access to
these files.

With the advent of network namespaces, various information relating to the network
stack is virtualized (see network_namespaces(7)). Thus, since Linux 2.6.25, /proc/net
is a symbolic link to the directory /proc/self/net, which contains the same files and
directories as listed below. However, these files and directories now expose informa‐
tion for the network namespace of which the process is a member.

/proc/net/arp
This holds an ASCII readable dump of the kernel ARP table used for address resolu‐
tions. It will show both dynamically learned and preprogrammed ARP entries. The for‐
mat is:

IP address HW type Flags HW address Mask Device
192.168.0.50 0x1 0x2 00:50:BF:25:68:F3 * eth0
192.168.0.250 0x1 0xc 00:00:00:00:00:00 * eth0

Here "IP address" is the IPv4 address of the machine and the "HW type" is the hardware
type of the address from RFC 826. The flags are the internal flags of the ARP struc‐
ture (as defined in /usr/include/linux/if_arp.h) and the "HW address" is the data link
layer mapping for that IP address if it is known.

/proc/net/dev
The dev pseudo-file contains network device status information. This gives the number
of received and sent packets, the number of errors and collisions and other basic sta‐
tistics. These are used by the ifconfig(8) program to report device status. The for‐
mat is:

Inter-| Receive | Transmit
face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed
lo: 2776770 11307 0 0 0 0 0 0 2776770 11307 0 0 0 0 0 0
eth0: 1215645 2751 0 0 0 0 0 0 1782404 4324 0 0 0 427 0 0
ppp0: 1622270 5552 1 0 0 0 0 0 354130 5669 0 0 0 0 0 0
tap0: 7714 81 0 0 0 0 0 0 7714 81 0 0 0 0 0 0

/proc/net/dev_mcast
Defined in /usr/src/linux/net/core/dev_mcast.c:

indx interface_name dmi_u dmi_g dmi_address
2 eth0 1 0 01005e000001
3 eth1 1 0 01005e000001
4 eth2 1 0 01005e000001

/proc/net/igmp
Internet Group Management Protocol. Defined in /usr/src/linux/net/core/igmp.c.

/proc/net/rarp
This file uses the same format as the arp file and contains the current reverse map‐
ping database used to provide rarp(8) reverse address lookup services. If RARP is not
configured into the kernel, this file will not be present.

/proc/net/raw
Holds a dump of the RAW socket table. Much of the information is not of use apart
from debugging. The "sl" value is the kernel hash slot for the socket, the "local_ad‐
dress" is the local address and protocol number pair. "St" is the internal status of
the socket. The "tx_queue" and "rx_queue" are the outgoing and incoming data queue in
terms of kernel memory usage. The "tr", "tm->when", and "rexmits" fields are not used
by RAW. The "uid" field holds the effective UID of the creator of the socket.

/proc/net/snmp
This file holds the ASCII data needed for the IP, ICMP, TCP, and UDP management infor‐
mation bases for an SNMP agent.

/proc/net/tcp
Holds a dump of the TCP socket table. Much of the information is not of use apart
from debugging. The "sl" value is the kernel hash slot for the socket, the "local_ad‐
dress" is the local address and port number pair. The "rem_address" is the remote ad‐
dress and port number pair (if connected). "St" is the internal status of the socket.
The "tx_queue" and "rx_queue" are the outgoing and incoming data queue in terms of
kernel memory usage. The "tr", "tm->when", and "rexmits" fields hold internal infor‐
mation of the kernel socket state and are useful only for debugging. The "uid" field
holds the effective UID of the creator of the socket.

/proc/net/udp
Holds a dump of the UDP socket table. Much of the information is not of use apart
from debugging. The "sl" value is the kernel hash slot for the socket, the "local_ad‐
dress" is the local address and port number pair. The "rem_address" is the remote ad‐
dress and port number pair (if connected). "St" is the internal status of the socket.
The "tx_queue" and "rx_queue" are the outgoing and incoming data queue in terms of
kernel memory usage. The "tr", "tm->when", and "rexmits" fields are not used by UDP.
The "uid" field holds the effective UID of the creator of the socket. The format is:

sl local_address rem_address st tx_queue rx_queue tr rexmits tm->when uid
1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

/proc/net/unix
Lists the UNIX domain sockets present within the system and their status. The format
is:

Num RefCount Protocol Flags Type St Inode Path
0: 00000002 00000000 00000000 0001 03 42
1: 00000001 00000000 00010000 0001 01 1948 /dev/printer

The fields are as follows:

Num: the kernel table slot number.

RefCount: the number of users of the socket.

Protocol: currently always 0.

Flags: the internal kernel flags holding the status of the socket.

Type: the socket type. For SOCK_STREAM sockets, this is 0001; for SOCK_DGRAM
sockets, it is 0002; and for SOCK_SEQPACKET sockets, it is 0005.

St: the internal state of the socket.

Inode: the inode number of the socket.

Path: the bound pathname (if any) of the socket. Sockets in the abstract name‐
space are included in the list, and are shown with a Path that commences
with the character '@'.

/proc/net/netfilter/nfnetlink_queue
This file contains information about netfilter user-space queueing, if used. Each
line represents a queue. Queues that have not been subscribed to by user space are
not shown.

1 4207 0 2 65535 0 0 0 1
(1) (2) (3)(4) (5) (6) (7) (8)

The fields in each line are:

(1) The ID of the queue. This matches what is specified in the --queue-num or
--queue-balance options to the iptables(8) NFQUEUE target. See iptables-exten‐
sions(8) for more information.

(2) The netlink port ID subscribed to the queue.

(3) The number of packets currently queued and waiting to be processed by the appli‐
cation.

(4) The copy mode of the queue. It is either 1 (metadata only) or 2 (also copy pay‐
load data to user space).

(5) Copy range; that is, how many bytes of packet payload should be copied to user
space at most.

(6) queue dropped. Number of packets that had to be dropped by the kernel because
too many packets are already waiting for user space to send back the mandatory
accept/drop verdicts.

(7) queue user dropped. Number of packets that were dropped within the netlink sub‐
system. Such drops usually happen when the corresponding socket buffer is full;
that is, user space is not able to read messages fast enough.

(8) sequence number. Every queued packet is associated with a (32-bit) monotonically
increasing sequence number. This shows the ID of the most recent packet queued.

The last number exists only for compatibility reasons and is always 1.

man > proc_net(5)