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nsenter: simplify netlink parsing

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This just moves everything to one function so we don't have to pass a
bunch of things to functions when there's no real benefit. It also makes
the API nicer.

Signed-off-by: Aleksa Sarai <asarai@suse.de>
This commit is contained in:
Aleksa Sarai
2016-07-20 23:53:58 +10:00
parent faa3281ce8
commit 4e72ffc237
1 changed files with 54 additions and 41 deletions
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libcontainer/nsenter/nsexec.c
+54 -41
View File
@@ -37,7 +37,8 @@ struct clone_arg {
jmp_buf *env;
};
struct nsenter_config {
struct nlconfig_t {
char *data;
uint32_t cloneflags;
char *uidmap;
int uidmap_len;
@@ -226,7 +227,7 @@ static void update_gidmap(int pid, char *map, int map_len)
#define JSON_MAX 4096
static void start_child(int pipenum, jmp_buf *env, int syncpipe[2], struct nsenter_config *config)
static void start_child(int pipenum, jmp_buf *env, int syncpipe[2], struct nlconfig_t *config)
{
int len, childpid;
char buf[JSON_MAX];
@@ -264,13 +265,37 @@ static void start_child(int pipenum, jmp_buf *env, int syncpipe[2], struct nsent
exit(0);
}
static struct nsenter_config process_nl_attributes(int pipenum, char *data, int data_size)
static void nl_parse(int fd, struct nlconfig_t *config)
{
char *current = data;
struct nsenter_config config = { 0 };
size_t len, size;
struct nlmsghdr hdr;
char *data, *current;
config.consolefd = -1;
while (current < data + data_size) {
/* Retrieve the netlink header. */
len = read(fd, &hdr, NLMSG_HDRLEN);
if (len != NLMSG_HDRLEN)
bail("invalid netlink header length %lu", len);
if (hdr.nlmsg_type == NLMSG_ERROR)
bail("failed to read netlink message");
if (hdr.nlmsg_type != INIT_MSG)
bail("unexpected msg type %d", hdr.nlmsg_type);
/* Retrieve data. */
size = NLMSG_PAYLOAD(&hdr, 0);
current = data = malloc(size);
if (!data)
bail("failed to allocate %d bytes of memory for nl_payload", size);
len = read(fd, data, size);
if (len != size)
bail("failed to read netlink payload, %lu != %lu", len, size);
/* Parse the netlink payload. */
config->data = data;
config->consolefd = -1;
while (current < data + size) {
struct nlattr *nlattr = (struct nlattr *)current;
size_t payload_len = nlattr->nla_len - NLA_HDRLEN;
@@ -280,7 +305,7 @@ static struct nsenter_config process_nl_attributes(int pipenum, char *data, int
/* Handle payload. */
switch (nlattr->nla_type) {
case CLONE_FLAGS_ATTR:
config.cloneflags = readint32(current);
config->cloneflags = readint32(current);
break;
case CONSOLE_PATH_ATTR:
/*
@@ -290,8 +315,8 @@ static struct nsenter_config process_nl_attributes(int pipenum, char *data, int
* decided here, but rather in container_linux.go. We just
* follow the order given by the netlink message.
*/
config.consolefd = open(current, O_RDWR);
if (config.consolefd < 0)
config->consolefd = open(current, O_RDWR);
if (config->consolefd < 0)
bail("failed to open console %s", current);
break;
case NS_PATHS_ATTR:{
@@ -340,18 +365,20 @@ static struct nsenter_config process_nl_attributes(int pipenum, char *data, int
close(fd);
}
free(fds);
free(paths);
break;
}
case UIDMAP_ATTR:
config.uidmap = current;
config.uidmap_len = payload_len;
config->uidmap = current;
config->uidmap_len = payload_len;
break;
case GIDMAP_ATTR:
config.gidmap = current;
config.gidmap_len = payload_len;
config->gidmap = current;
config->gidmap_len = payload_len;
break;
case SETGROUP_ATTR:
config.is_setgroup = readint8(current);
config->is_setgroup = readint8(current);
break;
default:
bail("unknown netlink message type %d", nlattr->nla_type);
@@ -359,13 +386,19 @@ static struct nsenter_config process_nl_attributes(int pipenum, char *data, int
current += NLA_ALIGN(payload_len);
}
}
return config;
void nl_free(struct nlconfig_t *config)
{
free(config->data);
}
void nsexec(void)
{
int pipenum;
jmp_buf env;
int syncpipe[2];
struct nlconfig_t config = {0};
/*
* If we don't have an init pipe, just return to the go routine.
@@ -375,31 +408,8 @@ void nsexec(void)
if (pipenum == -1)
return;
/* Retrieve the netlink header. */
int len;
struct nlmsghdr hdr;
len = read(pipenum, &hdr, NLMSG_HDRLEN);
if (len != NLMSG_HDRLEN)
bail("invalid netlink header length %d", len);
if (hdr.nlmsg_type == NLMSG_ERROR)
bail("failed to read netlink message");
if (hdr.nlmsg_type != INIT_MSG)
bail("unexpected msg type %d", hdr.nlmsg_type);
/* Retrieve data. */
size_t size = NLMSG_PAYLOAD(&hdr, 0);
char *data = alloca(size);
len = read(pipenum, data, size);
if (len != size)
bail("failed to read netlink payload, %d != %lu", len, size);
jmp_buf env;
int syncpipe[2];
struct nsenter_config config = process_nl_attributes(pipenum, data, size);
/* Parse all of the netlink configuration. */
nl_parse(pipenum, &config);
/* clone(2) flags are mandatory. */
if (config.cloneflags == -1)
@@ -448,6 +458,9 @@ void nsexec(void)
bail("failed to dup stderr");
}
/* Free netlink data. */
nl_free(&config);
/* Finish executing, let the Go runtime take over. */
return;
}