.TH mtcp_sendpkt 3 2017-08-27 "Linux" "mOS Library Functions Manual"
.SH NAME
mtcp_sendpkt \- Sends a self-constructed TCP packet to network
.SH SYNOPSIS
.B #include <mos_api.h>
.sp
.BI "int mtcp_sendpkt(mctx_t " mctx ", int " sockid ", struct pkt_info *" pinfo );

.SH DESCRIPTION
.BR mtcp_sendpkt () 
sends a self-constructed TCP packet for a given flow to network.
The user can select the socket descriptor using
.I "sockid"
and the
.I "pinfo"
points to an instance of
.BR struct 
pkt_info that is allocated and filled by the user via mtcp_getlastpkt() function.
It is the user's responsibility to allocate the
.I "pkt_info"
structure before the function call, and
free the
.I "pkt_info"
after the function call.
The structure is defined as:
.PP
 struct pkt_info {
 	// pkt recving time
 	uint32_t cur_ts;
 	// ETH
 	uint16_t eth_len;
 	// IP
 	uint16_t ip_len;
 	//TCP
 	uint64_t offset; // TCP recv buffer offset
 	uint16_t payloadlen;
 	uint32_t seq;
 	uint32_t ack_seq;
 	uint16_t window;

	struct ethhdr *ethh;
 	struct iphdr *iph;
 	struct tcphdr *tcph;
 	uint8_t *payload;
 	
 }
.PP
A successful call to
.BR mtcp_sendpkt()
constructs a TCP packet based on the given packet information
.I "pinfo"
and send the packet to the network.

An 
.BR mtcp_sendpkt()
call takes an additional argument named 
.I "mctx"
that represents the per-core mTCP context in an application
(see
.BR mtcp_create_context()
for details).
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.SH RETURN VALUE
Returns 0 on success; -1 on failure. In case
of failure,
.I "errno"
is set appropriately. 
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.SH ERRORS
.TP 15
.B "EACCES"
.I "mctx"
is invalid, or
.I "pinfo"
is NULL.

.TP 15
.B "ENODATA"
The packet information does not contain a valid IP header or
TCP header information. This normally does not occur when
we put the result of the
.BR "mtcp_sendpkt()"
function. Therefore, it means that the user modified the
packet information inappropriately.


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.\""""".SH CONFORMING TO
.\"""""POSIX.1-2001.
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.SH AUTHORS
mOS development team <mtcp-user@list.ndsl.kaist.edu>
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.SH SEE ALSO
.BR mtcp_create_context (),
.BR mtcp_setlastpkt (),
.BR mtcp_socket (),
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.SH COLOPHON
This page is part of mOS release 0.3
.I "docs"
section. A description of the project, and information
about reporting bugs, can be found at
\%http://mos.kaist.edu/.
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