In reworking the packet code, one point I'm not clear on is how the
linux-generic raw socket I/O model is supposed to deal with segmented
packets on both receive and transmit paths.
Transmit is presumably more straightforward. Here's a snippet from
odp_packet_socket.c (routine
while (i < len) { pkt = pkt_table[i]; frame = odp_packet_l2(pkt); frame_len
= odp_packet_get_len(pkt); ret = send(sockfd, frame, frame_len, flags); if
(odp_unlikely(ret == -1)) { if (odp_likely(errno == EAGAIN)) { flags = 0; /*
blocking for next rounds */ continue; /* resend buffer */ } else { break; }
} i++; } /* end while */
The current code assumes that it has contiguous addressability to the
entire packet. Is that a requirement of the raw socket interface? If not
then it would seem this could be replaced by the following more general
code:
while (i < len) {
pkt = pkt_table[i];
frame_len = odp_packet_len(pkt);
frame_offset = 0;
while (frame_len > 0) {
frame = odp_packet_offset_map(pkt,frame_offset,&seglen);
if (frame == NULL)
break;
ret = send(sockfd, frame, seg_len, flags);
if (odp_unlikely(ret == -1)) {
if (odp_likely(errno == EAGAIN)) {
flags = 0; /* blocking for next rounds */
continue; /* resend buffer */
} else {
frame_offset += seg_len;
frame_len -= seg_len;
}
}
}
i++;
} /* end while */
Would this code be functionally correct from a raw socket perspective?
Receive processing has similar issues. I've not been able to find any raw
socket examples (via googling) that don't assume they can receive an entire
packet into a single contiguous buffer. Is that a requirement of the
interface?
Is there support for scatter/gather lists in these APIs? If so then we may
need some additional ODP APIs (possibly internal) to allow the segment
lists to be manipulated as a whole rather than one-by-one.
Thanks.
Bill
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