kaffa/XDP-Firewall
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Implement support for LibXDP and improve code.

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This commit is contained in:
Christian Deacon
2023-06-06 21:20:19 +00:00
parent b77246c7ad
commit d088b4b157
2 changed files with 124 additions and 149 deletions
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189
src/xdpfw.c
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@@ -18,6 +18,7 @@
#include <bpf.h>
#include <libbpf.h>
#include <xdp/libxdp.h>
#include "xdpfw.h"
#include "config.h"
@@ -106,17 +107,25 @@ int updateconfig(struct config *cfg, char *cfgfile)
/**
* Finds a BPF map's FD.
*
* @param bpf_obj A pointer to the BPF object.
* @param prog A pointer to the XDP program structure.
* @param mapname The name of the map to retrieve.
*
* @return The map's FD.
*/
int findmapfd(struct bpf_object *bpf_obj, const char *mapname)
int findmapfd(struct xdp_program *prog, const char *mapname)
{
struct bpf_map *map;
int fd = -1;
map = bpf_object__find_map_by_name(bpf_obj, mapname);
struct bpf_object *obj = xdp_program__bpf_obj(prog);
if (obj == NULL)
{
fprintf(stderr, "Error finding BPF object from XDP program.\n");
goto out;
}
struct bpf_map *map = bpf_object__find_map_by_name(obj, mapname);
if (!map)
{
@@ -136,160 +145,117 @@ int findmapfd(struct bpf_object *bpf_obj, const char *mapname)
*
* @param filename The path to the BPF object file.
*
* @return BPF's program FD.
* @return XDP program structure (pointer) or NULL.
*/
int loadbpfobj(const char *filename, __u8 offload, int ifidx)
struct xdp_program *loadbpfobj(const char *filename)
{
int fd = -1;
struct xdp_program *prog = xdp_program__open_file(filename, "xdp_prog", NULL);
// Create attributes and assign XDP type + file name.
struct bpf_prog_load_attr attrs =
if (prog == NULL)
{
.prog_type = BPF_PROG_TYPE_XDP,
};
// If we want to offload the XDP program, we must send the ifindex item to the interface's index.
if (offload)
{
attrs.ifindex = ifidx;
}
attrs.file = filename;
// Check if we can access the BPF object file.
if (access(filename, O_RDONLY) < 0)
{
fprintf(stderr, "Could not read/access BPF object file :: %s (%s).\n", filename, strerror(errno));
return fd;
// The main function handles this error.
return NULL;
}
struct bpf_object *obj = NULL;
int err;
// Load the BPF object file itself.
err = bpf_prog_load_xattr(&attrs, &obj, &fd);
if (err)
{
fprintf(stderr, "Could not load XDP BPF program :: %s.\n", strerror(errno));
return fd;
}
struct bpf_program *prog;
// Load the BPF program itself by section name and try to retrieve FD.
prog = bpf_object__find_program_by_title(obj, "xdp_prog");
fd = bpf_program__fd(prog);
if (fd < 0)
{
printf("XDP program not found by section/title :: xdp_prog (%s).\n", strerror(fd));
return fd;
}
// Retrieve BPF maps.
filtersmap = findmapfd(obj, "filters_map");
statsmap = findmapfd(obj, "stats_map");
return fd;
return prog;
}
/**
* Attempts to attach or detach (progfd = -1) a BPF/XDP program to an interface.
*
* @param prog A pointer to the XDP program structure.
* @param ifidx The index to the interface to attach to.
* @param progfd A file description (FD) to the BPF/XDP program.
* @param detach If above 0, attempts to detach XDP program.
* @param cmd A pointer to a cmdline struct that includes command line arguments (mostly checking for offload/HW mode set).
*
* @return Returns the flag (int) it successfully attached the BPF/XDP program with or a negative value for error.
* @return 0 on success and 1 on error.
*/
int attachxdp(int ifidx, int progfd, struct cmdline *cmd)
int attachxdp(struct xdp_program *prog, int ifidx, __u8 detach, struct cmdline *cmd)
{
int err;
__u32 mode = XDP_MODE_NATIVE;
char *smode;
__u32 flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
__u32 mode = XDP_FLAGS_DRV_MODE;
smode = "DRV/native";
if (cmd->offload)
{
smode = "HW/offload";
mode = XDP_FLAGS_HW_MODE;
mode = XDP_MODE_HW;
}
else if (cmd->skb)
{
smode = "SKB/generic";
mode = XDP_FLAGS_SKB_MODE;
mode = XDP_MODE_SKB;
}
flags |= mode;
int exit = 0;
__u8 exit = 0;
while (!exit)
{
// Try loading program with current mode.
int err;
err = bpf_set_link_xdp_fd(ifidx, progfd, flags);
if (err || progfd == -1)
if (detach)
{
const char *errmode;
err = xdp_program__detach(prog, ifidx, mode, 0);
}
else
{
err = xdp_program__attach(prog, ifidx, mode, 0);
}
if (err)
{
if (err)
{
fprintf(stderr, "Could not attach with mode %s (%s) (%d).\n", smode, strerror(-err), -err);
}
// Decrease mode.
switch (mode)
{
case XDP_FLAGS_HW_MODE:
mode = XDP_FLAGS_DRV_MODE;
flags &= ~XDP_FLAGS_HW_MODE;
errmode = "HW/offload";
case XDP_MODE_HW:
mode = XDP_MODE_NATIVE;
smode = "DRV/native";
break;
case XDP_FLAGS_DRV_MODE:
mode = XDP_FLAGS_SKB_MODE;
flags &= ~XDP_FLAGS_DRV_MODE;
errmode = "DRV/native";
case XDP_MODE_NATIVE:
mode = XDP_MODE_SKB;
smode = "SKB/generic";
break;
case XDP_FLAGS_SKB_MODE:
// Exit program and set mode to -1 indicating error.
case XDP_MODE_SKB:
// Exit loop.
exit = 1;
mode = -err;
errmode = "SKB/generic";
smode = NULL;
break;
}
if (progfd != -1)
{
fprintf(stderr, "Could not attach with %s mode (%s)(%d).\n", errmode, strerror(-err), err);
}
if (mode != -err)
{
smode = (mode == XDP_FLAGS_HW_MODE) ? "HW/offload" : (mode == XDP_FLAGS_DRV_MODE) ? "DRV/native" : (mode == XDP_FLAGS_SKB_MODE) ? "SKB/generic" : "N/A";
flags |= mode;
}
}
else
{
fprintf(stdout, "Loaded XDP program in %s mode.\n", smode);
break;
// Retry.
continue;
}
// Success, so break current loop.
break;
}
return mode;
// If exit is set to 1 or smode is NULL, it indicates full failure.
if (exit || smode == NULL)
{
fprintf(stderr, "Error attaching XDP program.\n");
return 1;
}
fprintf(stdout, "Loaded XDP program on mode %s.\n", smode);
return 0;
}
struct stat conf_stat;
@@ -452,13 +418,12 @@ int main(int argc, char *argv[])
}
// XDP variables.
int progfd;
const char *filename = "/etc/xdpfw/xdpfw_kern.o";
// Get XDP's ID.
progfd = loadbpfobj(filename, cmd.offload, ifidx);
// Load BPF object.
struct xdp_program *prog = loadbpfobj(filename);
if (progfd <= 0)
if (prog == NULL)
{
fprintf(stderr, "Error loading eBPF object file. File name => %s.\n", filename);
@@ -466,15 +431,15 @@ int main(int argc, char *argv[])
}
// Attach XDP program.
int res = attachxdp(ifidx, progfd, &cmd);
if (res != XDP_FLAGS_HW_MODE && res != XDP_FLAGS_DRV_MODE && res != XDP_FLAGS_SKB_MODE)
if (attachxdp(prog, ifidx, 0, &cmd))
{
fprintf(stderr, "Error attaching XDP program :: %s (%d)\n", strerror(res), res);
return EXIT_FAILURE;
}
// Retrieve BPF maps.
filtersmap = findmapfd(prog, "filters_map");
statsmap = findmapfd(prog, "stats_map");
// Check for valid maps.
if (filtersmap < 0)
{
@@ -578,7 +543,7 @@ int main(int argc, char *argv[])
}
// Detach XDP program.
attachxdp(ifidx, -1, &cmd);
attachxdp(prog, ifidx, 1, &cmd);
// Add spacing.
fprintf(stdout, "\n");