-
Notifications
You must be signed in to change notification settings - Fork 0
/
fd.c
252 lines (222 loc) · 5.94 KB
/
fd.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
#include <nsocker/fd.h>
#include "fd.h"
#include <sys/socket.h>
#include <sys/uio.h>
#include <sys/types.h>
#include <stddef.h>
#include <errno.h>
#include <assert.h>
#include <stdio.h>
#include <string.h>
// https://keithp.com/blogs/fd-passing/
// https://unix.stackexchange.com/questions/185011/what-happens-with-unix-stream-ancillary-data-on-partial-reads
static void init_send_ioptr(struct iovec io[], iov_ptr* ioptr, ns_hdr *hdr, void *body, size_t body_size);
static void pull_ioptr(iov_ptr* ioptr, size_t size);
static bool is_ioptr_complete(iov_ptr *ioptr);
static bool would_block(bool *is_complete);
bool recv_junk(msg_reader *buf);
enum {IOV_HDR, IOV_BODY};
void ns_hdr_set(ns_hdr *hdr, ns_cmd cmd, size_t body_size)
{
hdr->id = htobe32(0);
hdr->cmd = htobe32(cmd);
hdr->size = htobe32(body_size + sizeof(*hdr));
}
static void init_send_ioptr(struct iovec io[], iov_ptr* ioptr, ns_hdr *hdr, void *body, size_t body_size)
{
io[IOV_HDR].iov_base = hdr;
io[IOV_HDR].iov_len = sizeof(*hdr);
io[IOV_BODY].iov_base = body;
io[IOV_BODY].iov_len = body_size;
ioptr->count = 2;
ioptr->ptr = &io[0];
}
static void pull_ioptr(iov_ptr* ioptr, size_t size)
{
while (size > 0) {
assert(ioptr->count != 0);
size_t chunk = size;
if (chunk > ioptr->ptr->iov_len)
chunk = ioptr->ptr->iov_len;
size -= chunk;
ioptr->ptr->iov_len -= chunk;
ioptr->ptr->iov_base += chunk;
if (ioptr->ptr->iov_len == 0) {
ioptr->ptr++;
ioptr->count--;
}
}
}
static bool is_ioptr_complete(iov_ptr *ioptr)
{
return ioptr->count == 0;
}
void ns_send_start(msg_writer *buf, int sockfd, ns_hdr* hdr, void* body, int fd)
{
size_t size = be32toh(hdr->size);
assert(size >= sizeof(*hdr));
size -= sizeof(*hdr);
buf->hdr = hdr;
buf->sockfd = sockfd;
buf->fd = fd;
buf->complete = false;
init_send_ioptr(buf->io, &buf->ioptr, hdr, body, size);
}
static bool would_block(bool *is_complete)
{
if (errno == EWOULDBLOCK) {
*is_complete = false;
return true;
} else {
return false;
}
}
bool ns_send(msg_writer *buf)
{
assert(!is_ioptr_complete(&buf->ioptr));
assert(!buf->complete);
struct msghdr msg;
struct cmsghdr *cmsg;
char cbuf[CMSG_SPACE(sizeof(int))];
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_iov = buf->ioptr.ptr;
msg.msg_iovlen = buf->ioptr.count;
msg.msg_flags = 0;
if (buf->fd >= 0) {
bzero(cbuf, sizeof(cbuf));
msg.msg_control = cbuf;
msg.msg_controllen = CMSG_SPACE(sizeof(int));
cmsg = CMSG_FIRSTHDR(&msg);
assert(cmsg);
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
*(int*)CMSG_DATA(cmsg) = buf->fd;
} else {
msg.msg_control = NULL;
msg.msg_controllen = 0;
}
ssize_t sent = sendmsg(buf->sockfd, &msg, 0);
if (sent < 0)
return would_block(&buf->complete);
pull_ioptr(&buf->ioptr, sent);
buf->fd = NS_NULL_FD;
buf->complete = is_ioptr_complete(&buf->ioptr);
return true;
}
bool ns_send_blocking(int sockfd, ns_hdr* hdr, void* body, int fd)
{
msg_writer buf;
bool error;
ns_send_start(&buf, sockfd, hdr, body, fd);
do {
error = ns_send(&buf);
} while (!error && !buf.complete);
return error;
}
#define JUNK_AT_TIME 0x100
static char junkbuf[JUNK_AT_TIME];
void ns_recv_start(msg_reader *buf, int sockfd, ns_hdr* hdr, void* body, size_t body_size, int *fd)
{
buf->hdr = hdr;
buf->sockfd = sockfd;
buf->fd = fd;
buf->recv_count = 0;
buf->body_buf_size = body_size;
buf->hdr_received = false;
buf->junk_remaining = 0;
buf->complete = false;
if (fd)
*fd = NS_NULL_FD;
buf->ioptr.ptr = buf->io;
buf->ioptr.count = 1;
buf->io[IOV_HDR].iov_base = hdr;
buf->io[IOV_HDR].iov_len = sizeof(*hdr);
buf->io[IOV_BODY].iov_base = body;
}
bool recv_junk(msg_reader *buf)
{
size_t junk_size = (buf->junk_remaining > JUNK_AT_TIME) ? JUNK_AT_TIME : buf->junk_remaining;
ssize_t received = recv(buf->sockfd, junkbuf, junk_size, 0);
if (received < 0)
return would_block(&buf->complete);
buf->junk_remaining -= received;
buf->complete = buf->junk_remaining == 0;
errno = EPROTO;
return false;
}
bool ns_recv(msg_reader *buf)
{
assert(!buf->complete);
if (buf->junk_remaining)
return recv_junk(buf);
struct msghdr msg;
struct cmsghdr *cmsg;
char cbuf[CMSG_SPACE(sizeof(int))];
// to the receive, optionally accepting the fd
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_iov = buf->ioptr.ptr;
msg.msg_iovlen = buf->ioptr.count;
msg.msg_flags = 0;
if (buf->fd) {
bzero(cbuf, sizeof(cbuf));
msg.msg_control = cbuf;
msg.msg_controllen = CMSG_LEN(sizeof(int));
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_len = CMSG_LEN(sizeof(int));
cmsg->cmsg_level = SOL_SOCKET;
cmsg->cmsg_type = SCM_RIGHTS;
} else {
msg.msg_control = NULL;
msg.msg_controllen = 0;
}
ssize_t received = recvmsg(buf->sockfd, &msg, 0);
if (received < 0)
return would_block(&buf->complete);
if (received == 0) {
errno = 0;
buf->eof = true;
return false;
}
pull_ioptr(&buf->ioptr, received);
if (buf->fd) {
cmsg = CMSG_FIRSTHDR(&msg);
if (cmsg && cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS
&& cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
*buf->fd = *(int*)CMSG_DATA(cmsg);
buf->fd = NULL;
}
}
// have we received the header? we need to get ready for more data
buf->recv_count += received;
if (buf->recv_count >= sizeof(ns_hdr) && !buf->hdr_received) {
buf->hdr_received = true;
size_t size = be32toh(buf->hdr->size);
if (size < sizeof(ns_hdr)) {
errno = EPROTO;
return false;
}
size -= sizeof(ns_hdr);
// larger than expected? start treating everything like junk
if (size > buf->body_buf_size) {
buf->junk_remaining = size;
return true;
}
buf->io[IOV_BODY].iov_len = size;
buf->ioptr.count++;
}
buf->complete = is_ioptr_complete(&buf->ioptr);
return true;
}
bool ns_recv_blocking(int sockfd, ns_hdr* hdr, void *body, size_t body_size, int *fd, bool *eof){
msg_reader buf;
bool ok;
ns_recv_start(&buf, sockfd, hdr, body, body_size, fd);
do {
ok = ns_recv(&buf);
} while (ok && !buf.complete);
*eof = buf.eof;
return ok;
}