SYNOPSIS<\/a>
DESCRIPTION<\/a>
ERRORS<\/a>
VERSIONS<\/a>
NOTES<\/a>
BUGS<\/a>
SEE ALSO<\/a>
COLOPHON<\/a> <\/p>\n
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NAME <\/a> <\/h2>\nraw \u2212 Linux IPv4 raw sockets<\/p>\n
SYNOPSIS <\/a> <\/h2>\n#include
#include
raw_socket = socket(AF_INET, SOCK_RAW, int<\/b> protocol<\/i>);<\/b><\/p>\nDESCRIPTION <\/a> <\/h2>\nRaw sockets allow new IPv4 protocols to be implemented in user space. A raw socket receives or sends the raw datagram not including link level headers.<\/p>\n
The IPv4 layer generates an IP header when sending a packet unless the IP_HDRINCL<\/b> socket option is enabled on the socket. When it is enabled, the packet must contain an IP header. For receiving, the IP header is always included in the packet.<\/p>\n
In order to create a raw socket, a process must have the CAP_NET_RAW<\/b> capability in the user namespace that governs its network namespace.<\/p>\n
All packets or errors matching the protocol<\/i> number specified for the raw socket are passed to this socket. For a list of the allowed protocols, see the IANA list of assigned protocol numbers at http:\/\/www.iana.org\/assignments\/protocol-numbers\/<\/a> and getprotobyname<\/b>(3).<\/p>\nA protocol of IPPROTO_RAW<\/b> implies enabled IP_HDRINCL<\/b> and is able to send any IP protocol that is specified in the passed header. Receiving of all IP protocols via IPPROTO_RAW<\/b> is not possible using raw sockets.<\/p>\n
![\"Image](\"grohtml-931991.png\")
<\/p>\n
If IP_HDRINCL<\/b> is specified and the IP header has a nonzero destination address, then the destination address of the socket is used to route the packet. When MSG_DONTROUTE<\/b> is specified, the destination address should refer to a local interface, otherwise a routing table lookup is done anyway but gatewayed routes are ignored.<\/p>\n
If IP_HDRINCL<\/b> isn\u2019t set, then IP header options can be set on raw sockets with setsockopt<\/b>(2); see ip<\/b>(7) for more information.<\/p>\n
Starting with Linux 2.2, all IP header fields and options can be set using IP socket options. This means raw sockets are usually needed only for new protocols or protocols with no user interface (like ICMP).<\/p>\n
When a packet is received, it is passed to any raw sockets which have been bound to its protocol before it is passed to other protocol handlers (e.g., kernel protocol modules).<\/p>\n
Address format<\/b>
For sending and receiving datagrams (sendto<\/b>(2), recvfrom<\/b>(2), and similar), raw sockets use the standard sockaddr_in<\/i> address structure defined in ip<\/b>(7). The sin_port<\/i> field could be used to specify the IP protocol number, but it is ignored for sending in Linux 2.2 and later, and should be always set to 0 (see BUGS). For incoming packets, sin_port<\/i> is set to zero.<\/p>\n
Socket options<\/b>
Raw socket options can be set with setsockopt<\/b>(2) and read with getsockopt<\/b>(2) by passing the IPPROTO_RAW<\/b> family flag.
ICMP_FILTER<\/b><\/p>\n
Enable a special filter for raw sockets bound to the IPPROTO_ICMP<\/b> protocol. The value has a bit set for each ICMP message type which should be filtered out. The default is to filter no ICMP messages.<\/p>\n
In addition, all ip<\/b>(7) IPPROTO_IP<\/b> socket options valid for datagram sockets are supported.<\/p>\n
Error handling<\/b>
Errors originating from the network are passed to the user only when the socket is connected or the IP_RECVERR<\/b> flag is enabled. For connected sockets, only EMSGSIZE<\/b> and EPROTO<\/b> are passed for compatibility. With IP_RECVERR<\/b>, all network errors are saved in the error queue.<\/p>\nERRORS <\/a> <\/h2>\n
#include Raw sockets allow new IPv4 protocols to be implemented in user space. A raw socket receives or sends the raw datagram not including link level headers.<\/p>\n The IPv4 layer generates an IP header when sending a packet unless the IP_HDRINCL<\/b> socket option is enabled on the socket. When it is enabled, the packet must contain an IP header. For receiving, the IP header is always included in the packet.<\/p>\n In order to create a raw socket, a process must have the CAP_NET_RAW<\/b> capability in the user namespace that governs its network namespace.<\/p>\n All packets or errors matching the protocol<\/i> number specified for the raw socket are passed to this socket. For a list of the allowed protocols, see the IANA list of assigned protocol numbers at http:\/\/www.iana.org\/assignments\/protocol-numbers\/<\/a> and getprotobyname<\/b>(3).<\/p>\n A protocol of IPPROTO_RAW<\/b> implies enabled IP_HDRINCL<\/b> and is able to send any IP protocol that is specified in the passed header. Receiving of all IP protocols via IPPROTO_RAW<\/b> is not possible using raw sockets.<\/p>\n If IP_HDRINCL<\/b> is specified and the IP header has a nonzero destination address, then the destination address of the socket is used to route the packet. When MSG_DONTROUTE<\/b> is specified, the destination address should refer to a local interface, otherwise a routing table lookup is done anyway but gatewayed routes are ignored.<\/p>\n If IP_HDRINCL<\/b> isn\u2019t set, then IP header options can be set on raw sockets with setsockopt<\/b>(2); see ip<\/b>(7) for more information.<\/p>\n Starting with Linux 2.2, all IP header fields and options can be set using IP socket options. This means raw sockets are usually needed only for new protocols or protocols with no user interface (like ICMP).<\/p>\n When a packet is received, it is passed to any raw sockets which have been bound to its protocol before it is passed to other protocol handlers (e.g., kernel protocol modules).<\/p>\n Address format<\/b> Socket options<\/b> Enable a special filter for raw sockets bound to the IPPROTO_ICMP<\/b> protocol. The value has a bit set for each ICMP message type which should be filtered out. The default is to filter no ICMP messages.<\/p>\n In addition, all ip<\/b>(7) IPPROTO_IP<\/b> socket options valid for datagram sockets are supported.<\/p>\n Error handling<\/b>
#include
raw_socket = socket(AF_INET, SOCK_RAW, int<\/b> protocol<\/i>);<\/b><\/p>\nDESCRIPTION <\/a> <\/h2>\n
<\/p>\n
For sending and receiving datagrams (sendto<\/b>(2), recvfrom<\/b>(2), and similar), raw sockets use the standard sockaddr_in<\/i> address structure defined in ip<\/b>(7). The sin_port<\/i> field could be used to specify the IP protocol number, but it is ignored for sending in Linux 2.2 and later, and should be always set to 0 (see BUGS). For incoming packets, sin_port<\/i> is set to zero.<\/p>\n
Raw socket options can be set with setsockopt<\/b>(2) and read with getsockopt<\/b>(2) by passing the IPPROTO_RAW<\/b> family flag.
ICMP_FILTER<\/b><\/p>\n
Errors originating from the network are passed to the user only when the socket is connected or the IP_RECVERR<\/b> flag is enabled. For connected sockets, only EMSGSIZE<\/b> and EPROTO<\/b> are passed for compatibility. With IP_RECVERR<\/b>, all network errors are saved in the error queue.<\/p>\nERRORS <\/a> <\/h2>\n