Here's a diff that restructures packet handling to allow easier addition
of SNMPv3.
diff --git a/snmp.c b/snmp.c
index 7fac777..b2d5cfc 100644
--- a/snmp.c
+++ b/snmp.c
@@ -32,6 +32,10 @@
static struct ber_element *
snmp_resolve(struct snmp_agent *, struct ber_element *, int);
+static char *
+ snmp_package(struct snmp_agent *, struct ber_element *, size_t *);
+static struct ber_element *
+ snmp_unpackage(struct snmp_agent *, char *, size_t);
struct snmp_agent *
snmp_connect_v12(int fd, enum snmp_version version, const char *community)
@@ -171,19 +175,16 @@ fail:
static struct ber_element *
snmp_resolve(struct snmp_agent *agent, struct ber_element *pdu, int reply)
{
- struct ber_element *message, *varbind;
+ struct ber_element *varbind;
struct ber_oid oid;
struct timespec start, now;
struct pollfd pfd;
- struct ber ber;
+ char *message;
ssize_t len;
long long reqid, rreqid;
- long long version;
- char *community;
short direction;
int to, nfds, ret;
int tries;
- void *ptr;
char buf[READ_BUF_SIZE];
if (ber_scanf_elements(pdu, "{i", &reqid) != 0) {
@@ -192,23 +193,8 @@ snmp_resolve(struct snmp_agent *agent, struct ber_element
*pdu, int reply)
return NULL;
}
- if ((message = ber_add_sequence(NULL)) == NULL) {
- ber_free_elements(pdu);
- return NULL;
- }
- if (ber_printf_elements(message, "dse", agent->version,
- agent->community, pdu) == NULL) {
- ber_free_elements(pdu);
- ber_free_elements(message);
+ if ((message = snmp_package(agent, pdu, &len)) == NULL)
return NULL;
- }
- memset(&ber, 0, sizeof(ber));
- ber_set_application(&ber, smi_application);
- len = ber_write_elements(&ber, message);
- ber_free_elements(message);
- message = NULL;
- if (ber_get_writebuf(&ber, &ptr) < 1)
- goto fail;
clock_gettime(CLOCK_MONOTONIC, &start);
memcpy(&now, &start, sizeof(now));
@@ -236,7 +222,7 @@ snmp_resolve(struct snmp_agent *agent, struct ber_element
*pdu, int reply)
goto fail;
}
if (direction == POLLOUT) {
- ret = send(agent->fd, ptr, len, MSG_DONTWAIT);
+ ret = send(agent->fd, message, len, MSG_DONTWAIT);
if (ret == -1)
goto fail;
if (ret < len) {
@@ -253,25 +239,10 @@ snmp_resolve(struct snmp_agent *agent, struct ber_element
*pdu, int reply)
errno = ECONNRESET;
if (ret <= 0)
goto fail;
- ber_set_readbuf(&ber, buf, ret);
- if ((message = ber_read_elements(&ber, NULL)) == NULL) {
- direction = POLLOUT;
+ if ((pdu = snmp_unpackage(agent, buf, ret)) == NULL) {
tries--;
- continue;
- }
- if (ber_scanf_elements(message, "{ise", &version, &community,
- &pdu) != 0) {
- errno = EPROTO;
direction = POLLOUT;
- tries--;
- continue;
- }
- /* Skip invalid packets; should not happen */
- if (version != agent->version ||
- strcmp(community, agent->community) != 0) {
errno = EPROTO;
- direction = POLLOUT;
- tries--;
continue;
}
/* Validate pdu format and check request id */
@@ -297,17 +268,96 @@ snmp_resolve(struct snmp_agent *agent, struct ber_element
*pdu, int reply)
break;
}
}
- if (varbind != NULL)
- continue;
- ber_unlink_elements(message->be_sub->be_next);
- ber_free_elements(message);
- ber_free(&ber);
+ free(message);
return pdu;
}
+fail:
+ free(message);
+ return NULL;
+}
+
+static char *
+snmp_package(struct snmp_agent *agent, struct ber_element *pdu, size_t *len)
+{
+ struct ber ber;
+ struct ber_element *message;
+ ssize_t ret;
+ char *buf, *packet = NULL;
+
+ bzero(&ber, sizeof(ber));
+ ber_set_application(&ber, smi_application);
+
+ if ((message = ber_add_sequence(NULL)) == NULL) {
+ ber_free_elements(pdu);
+ goto fail;
+ }
+
+ switch (agent->version) {
+ case SNMP_V1:
+ case SNMP_V2C:
+ if (ber_printf_elements(message, "dse", agent->version,
+ agent->community, pdu) == NULL) {
+ ber_free_elements(pdu);
+ goto fail;
+ }
+ break;
+ case SNMP_V3:
+ break;
+ }
+
+ if ((ret = ber_write_elements(&ber, message)) == -1)
+ goto fail;
+ *len = (size_t) ret;
+ if (ber_get_writebuf(&ber, (void **)&buf) != -1 &&
+ (packet = malloc(ret)) != NULL)
+ memcpy(packet, buf, ret);
+ ber_free(&ber);
+
fail:
ber_free_elements(message);
+ return packet;
+}
+
+static struct ber_element *
+snmp_unpackage(struct snmp_agent *agent, char *buf, size_t buflen)
+{
+ struct ber ber;
+ enum snmp_version version;
+ char *community;
+ struct ber_element *pdu;
+ struct ber_element *message = NULL, *payload;
+
+ bzero(&ber, sizeof(ber));
+ ber_set_application(&ber, smi_application);
+
+ ber_set_readbuf(&ber, buf, buflen);
+ if ((message = ber_read_elements(&ber, NULL)) == NULL)
+ return NULL;
ber_free(&ber);
+
+ if (ber_scanf_elements(message, "{de", &version, &payload) != 0)
+ goto fail;
+
+ if (version != agent->version)
+ goto fail;
+
+ switch (version)
+ {
+ case SNMP_V1:
+ case SNMP_V2C:
+ if (ber_scanf_elements(payload, "se", &community, &pdu) == -1)
+ goto fail;
+ ber_unlink_elements(payload);
+ ber_free_elements(message);
+ return pdu;
+ case SNMP_V3:
+ break;
+ }
+ /* NOTREACHED */
+
+fail:
+ ber_free_elements(message);
return NULL;
}
diff --git a/snmpc.c b/snmpc.c
index dc48b10..104bb7c 100644
--- a/snmpc.c
+++ b/snmpc.c
@@ -45,6 +45,7 @@ int snmpc_get(int, char *[]);
int snmpc_walk(int, char *[]);
int snmpc_trap(int, char *[]);
int snmpc_mibtree(int, char *[]);
+struct snmp_agent *snmpc_connect(char *, char *);
int snmpc_parseagent(char *, char *);
int snmpc_print(struct ber_element *);
__dead void snmpc_printerror(enum snmp_error, char *);
@@ -304,9 +305,7 @@ snmpc_get(int argc, char *argv[])
if (argc < 2)
usage();
- agent = snmp_connect_v12(snmpc_parseagent(argv[0], "161"), version,
- community);
- if (agent == NULL)
+ if ((agent = snmpc_connect(argv[0], "161")) == NULL)
err(1, "%s", snmp_app->name);
agent->timeout = timeout;
agent->retries = retries;
@@ -372,8 +371,7 @@ snmpc_walk(int argc, char *argv[])
usage();
oids = argc == 1 ? mib : argv[1];
- agent = snmp_connect_v12(snmpc_parseagent(argv[0], "161"), version,
community);
- if (agent == NULL)
+ if ((agent = snmpc_connect(argv[0], "161"))== NULL)
err(1, "%s", snmp_app->name);
agent->timeout = timeout;
agent->retries = retries;
@@ -495,9 +493,7 @@ snmpc_trap(int argc, char *argv[])
if (version == SNMP_V1)
errx(1, "trap is not supported for snmp v1");
- agent = snmp_connect_v12(snmpc_parseagent(argv[0], "162"),
- version, community);
- if (agent == NULL)
+ if ((agent = snmpc_connect(argv[0], "162")) == NULL)
err(1, "%s", snmp_app->name);
if (pledge("stdio", NULL) == -1)
@@ -693,6 +689,18 @@ snmpc_mibtree(int argc, char *argv[])
return 0;
}
+struct snmp_agent *
+snmpc_connect(char *host, char *port)
+{
+ switch (version) {
+ case SNMP_V1:
+ case SNMP_V2C:
+ return snmp_connect_v12(snmpc_parseagent(host, port), version,
+ community);
+ }
+ return NULL;
+}
+
int
snmpc_print(struct ber_element *elm)
{
